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Revus Arachnologique , 1 (4) , 1978 : 133 * 164.

Comparative studies of Dictyna and Mallos
(Araneae, D)
I, social organization and web characteristics

by Robert R. JACKSON*
Contents
Résumé 134
Summary • •..134
Introduction •••.•••••…………………………… 135
Type of webs and social organisation •••••••*•••••••••••• 140
Individual webs. Solitary species ••••••«••••••••••••• 140
Web complexes. Communal, territorial species ……… 144
Communal webs. Communal, non*territorial species ••••• 144
Territoriality …………………………………..144
Web sites ……………………………………. 144
Geographical distribution and habitats •••••••••«•••••••• 146
Web size and geometry …………………•..•••.•••••••• 149
Individual webs 149
Web complexes •«••••••…………….. ••••……… 150
Communal webs ••••••••………………. •••••••••••• 151
Extension lines ……•••••••••…….••••••••••……… 151
Debris and prey remains in webs 151
Nests ……………………………….. •••….••• 151
Spacing of individual webs 154
Connected individual webs 154
Isolated webs of communal, territorial species .•.••••••• 154
Group size in M• gregalis ••••••••..••••…………….. 155
Groups of spiders sharing individual webs .••••••••••.••• 156
Sympatry among dictynid species •••••••••••••••••••••..•• 156
Longevity of webs •••••••………………………. 157
peneral discussion ……………………………… 158
Acknowledgement…………………………………… 160
References ………………..•••••………………… 161
♦Manuscrit reçu le 29 novembre 1977; adresse de lfauteur: Department of
Zoology, University of Canterbury, Christchurch 1, New Zealand.
JACKSON
Résumé
Les traits caractéristiques des toiles et les organisations sociales
de 20 espèces ont été comparés dans la nature» et quatre au laboratoire*
On trouve trois types de toiles et trois types correspondants dforganisa-*
tion sociale* La plupart des espèces sont solitaires; trois espèces sont
communales et territoriales (D. albopïlosa, D. calcarata, Af. trivittatue) ;
et une espèce est communale» non-territoriale (Af. gregalis) • Les espèces
solitaires vivent dans des toiles individuelles» chacune se composant
d’un nid et d’un réseau* A l’exception des paires» male et femelle» et
des femelles avec des enfants» on trouve une seule araignée par toile
individuelle» et les toiles de ces espèces ne sont pas liées ordinairement
aux autres toiles par de la soie* Les espèces communales et territoriales
vivent dans des complexes de toiles» chacun se composant d’un nombre’ vari-
able de toiles élémentaires (nid et réseau) qui sont liées les unes aux
autres par une toile interstitielle* Chaque élément de toile a tendance
à contenir un petit groupe d’araignées de classes de sexe ou d’age diffé-
rentes» et les occupants traitent les éléments de toile comme des terri-
toires* Dans l’espèce communale non-territoriale» plusieurs milliers
de toutes les classes de sexe et d’age habitent des toiles communes qui
ont des dimensions variables et qui ne se divisent pas en éléments de
toiles défendus* Cette espèce se nourrit régulièrement en groupes sur une
meme proie* Ordinairement» les individus d’autres espèces se nourrissent
isolément* Les sites des toiles varient è l’intérieur d’une meme espèce»
et les sites d’espèces d’organisation sociale différente s’interpénétrent*
Les emp lacement s des toiles sont la cause principale de leur forme* Beau-
coup de débris peuvent s’accumuler dans les toiles de tous types* La com-
préhension des traits caractéristiques des toiles de Dictyniâae semble
être étroitement lié à la compréhension des types d’organisation sociale
que l’on trouve chez ces espèces*
Summary
Web characteristics and social organisation of 20 species were comp-
ared in nature; four» in the laboratory* Three types of webs and three
corresponding types of social organisation occur • Host species are solitary;
three are communal» territorial (D* dlbopilosa» D. calcarata» Af* tnvittar
tue) i and one is communal» non-territorial (Af* gregalie) « Solitary species
live in individual webs» each consisting of a nest and a mesh* Except for
male-female pairs and females with offspring» one finds a single spider
per individual veb» and the webs of these species are usually not connec-
ted to other webs by silk* Communal» territorial species live in web com-
plexes» each consisting of a variable number of web units (nest and mesh
or sheet) which are connected to each other by interstitial web* Each
veb unit tends to contain a small group of spiders of differing sex/age
classes» and the occupants treat the veb units as territories* In the
communal» non-territorial species» up to several thousand individuals of
all sex/age classes occupy communal webs» which are variable in size and
which are not divided into defended web units* This species routinely feeds
in groups on single prey items* Usually individuals of the other species
feed alone* Web sites vary intraspecifically» and those of species with
different types of social organisation overlap* Web sites are major deter-
minants of veb shape. Much debris may accumulate in webs of all types*
Understanding dictynid web characteristics seems to be integral to under-
standing the types of social organisation found in these species.
Dictyna and Hallos
135
INTRODUCTION
Although most spiders are “solitary” there are certain species that
tend to live in groups, and some of these are referred to as “social spi-
ders”. The most extensively studied social species is Agelena coneociata
Denis (CHAUVIN and DENIS, 1965; DARCHEN, 1965, 1973, 1975, 1976; KRAFFT,
1969, 1970a, 1970b, 1971, 1975; PAIN, 1964). Some other important studies
have dealt with the social characteristics of eresid (KULLMANN, 1969;
KULLMANN et aim, 1972; KULLMANN and ZIMMERMANN, 1971), theridiid (BRACH,
1975, 1977; DARCHEN, 1968), and araneid (BLANKE, 1972; BUSKIRK, 1975;
LDBIN, 1974) spiders. The Dictynidae are another group of spiders with
social species. In particular, the Mexican species Malloe gvegaVis Simon
lives in large communal webs in vich hundreds of individuals peacefully
intensifie. DIGUET (1909 a, 1909 b, 1915), SEMICHON (1910), SIMON (1909)
and BERLAND (1913, 1928) initially brought this species to the attention
of scientific community, and BURGESS (1976) generated new interest. Howe-
ver, the social characteristics of other dictynid species have been largely
neglected.
A group of dictynid species, UaVloQ and Dictyna, were chosen for this
study because comments by CHAMBERLIN and GERTSCH (1958) suggested that
closely related species in these genera vary extensively in their social
characteristics. This opportunity for comparative studies would provide
means of clarifying which characteristics of Jf. gregalis are adaptations
related to social life. Dictyna is cosmopolitan in distribution. However,
Hallos is restricted to a region extending from Central America north
through the western parts of North America. Several months were spent in
the summer of 1976 in Mexico and parts of the western United States (table
1), during which time data were collected for all species of Mallos and
Dictyna that I could find in their natural habitats. Since the dictynids
are web-building spiders and because web-spiders tend to be highly speci-
alised in their adaptations related to life on a web (see PEAKALL, 1968,
e.g.), a working hypothesis was that knowledge of the webs of these spiders
would be integral to understanding their social organisation. Evidence of
this will be presented.
WILSON (1971) proposed a logical sequence of four central questions
in the study of social insects which might be profitably considered by
students of social spiders. Paraphrasing WILSON, this paper will concen-
trate primarily on the first two questions: what are the qualities of
social life in dictynid spiders, and how are dictynid “societies” organized?
Questions concerning evolutionary steps and selection factors can be mea-
ningfully investigated only after we have an understanding of social qua-
lities and social organisation.
The group of spiders for which the expression “social” is used seems
to be relatively clear. However, it is more problematical to provide defi-
nitions of spider sociality and categories of sociality because our know-
ledge of social phenomena in spiders is still in an early and changing
stage (for reviews, see BURGESS, 1976, 1978; KRAFFT, 1970; KULLMANN, 1968,
1972; SHEAR, 1970). In the early development of a science, some terms need
to remain flexible and be provided a chance to mature (BEER, 1977). This
seems to be the case with the term “social” when applied to spiders. WILSON
Cuernavaca MonloSi Mx. (la Cuernavaca) ISOO SI Buildings
Guanajaato Guanajaato, Mx. (in Guanajaato) 2000 m buildings
Juventinoa Rosas Guanajaato, Mx. (Juventinoa Roeaa) 2000 – 2500 si Herbs, Shrubs Flat
Lake Chapala Jalisco 4 Mlchoacan, Mx. tsoo ■
I* Chapala Jalisco (in Chapala) Buildings
2. Chula Vista Jalisco (Chapala) Herbs Flat
3. Cojuaetlan Michoacan (Cojunatlan) Herbs, shrubs Flat
4. Ixtlahuacan Jalisco (Ixtlahuacan da los Mem- brillos) Shrubs Gentle slope
Quoretaro Quaretaro, Mx. (Quarataro) 2000 ■ Herbs Flat
San Anton Falls Morelos, Mx. (Cuamavaca) 1500 m Herbs Vary steep, slope (canyon walls)
San Miquel de ÂïTende Guanajaato» Mx* (in San Miguel da Allende) 2000 n Buildings
Bandelier New Maxlco, USA (Bandaliar National Monu- scat) 2000 n Herbs, Shrubs Flat
Table 1
U>
O’
PLANT COMMUNITY BODIES OF WATER NUMEROUS DIPTERA TIME
2.2 M»E
2.4 D.E
Oak1 woodland 1.3 D
Ca* 100 n from laka Chironomids and other ntma- tocerous flies* M and especially E. 3.7 h.d.e
Cultivated tree* and shruba. Near notai and bouses Ca* 100 m from lake As at I 2.2 H.E
Scrub» cactus trees• Ca* 100 m from lake 1.2 D
Scrub Ca* 1 km iron lake U D
Non~cultivated area between alfafa and corn fields* Scattered shrubs and Aoaoia trees 1.1 D
Riverine forest» dense plant growth Adjacent to falls Various types 2.7 D
2.3
D.E
a. Desert» Saltbush3 a» Ce* 100 ■ from l(3
eraak D
b» Riverine forait b* Baaida eraak
(closed canopy)
Junipirue, Pirtui»
Cottonwood» \ ,
Boxa Ida ri 3,
JACKSON
Table 1
MAMX OP HABITAT LOCATION KLXVATION WEB SITES TERRAIN PLANT COMMUNITY BODIE8 OF HATER NUMEROUS DIPTERA TIME
Chiracahua Mountains I* ChiracahuA National Monument Arisons, USA Host sido of rants » (Chiracahua National Nomuasnt) 2000 a Shrubs Plat, vicinity of dry croak bod 8iailar to E» Turkay Crook Various typos, whore water present. M and especially X 1.3 D
2. Cava Croak East sida of 1500- Harbs, Plat or Siailar to E. Turkey Sporadic in crooks 6,18
Canyon rangs (Portal) 2000 a shrubs, rocks, boulders, buildings» Saotla slops Crook m 1 M,D,E
3. Eaat Turkay Croak East aids of rangs (Portal) 2000 a Harbs, shrubs, trass, rocks, bouldsrs, culvert* Cantla slops a. Oak woodland a» Bosido crook b. Along crook, b» Insido aotal forest (canopy culvsrt through alternately which crook flows open and clossd) Aliiaator juni- pers*. Especially in culvert 14,48 M,D,E
4. Portal East sido of rangs. Bass of nountains (Portal) 1500 a Harbs, Shrubs, (especially OutierrëMÎa) Plat » j Desert, Mesquite? 5,8 D
S. Rustler’s Park East aids of rangs (Portal) 2500 a Harbs, rock ladgss Plat and gontlo slopos Similar to E« Turkey Crook le» D
6. Vino Palis Dinosaur East aids of rangs (Portal) Utah, USA (Dinosaur National Monument) 2500 a 1500 a Rock ladga Shrubs Stoop slops Plat Vfoodland. Walnut** Ca. 100 m from crook and falls Desert, Sago9 a. Thick growth of a* Beside green of sago9 River b. Scattered sago9 b* Ca. 100 m from river 1,2 D M D
Flaming Gorge Utah, USA (Planing Corgo National Recre- atior aroa) 2000 a Trass, Rocks, Bouldsrs Gontlo slops Lodgepole pine*0 forest (closed canopy),t Aapen*. Culicidao 2,3 M,E
Gila Now Mexico, USA (Cila Cliff Dwell- ing National Monuaant) 2000 a Harbs, Shrubs Plat Scattered cotton- a. Bosido Host Pork woods^ and Junipers. of Gila River Desert shrubs b. Bosido dry crook bod (no water in aroa) 1.3 D
Diotyna and Malloa
Grand Teton Wyoming, USA (in Grand Taton National Park) East fide of Taton ranga
I. Climber’s Ranch Jackson Hole 2000 ■ Shrubs Plat
2. Garnet Canyon Just below timberline. Vicinity of Grand Taton 3000 a Shrubs Steep slopes
3. Leigh Lake Jackson Hole 2000 a Shrubs, trees Plat
Guadalupe Texas (in Guadalupe National Park) A New Mexico (In Carlsbad National Park) USA. East side of range Shrubs Plat
Querecho Plains New Mexico» USA 1000 a Shrubs Plat
Rocky Mountain Colorado, U8A (Rocky Mountain National Park) East of park
1. Big Thompson Canyon (Loveland) 2000 a Rock wall of canyon Preci- pitous
2. Eataa Park (Estes Park) Herbs, * Rock ledge Gentle slope
3. St. Vrain North Branch of tha St. Vrain creak 2500- 3000 a Shrubs
Table 1
PUNT COMMUNITY BODIES OP HATER NUMEROUS DIPTERA TIME
Ntidov with icittind 3,6
cottonwood**, willow1* M,D,E
shrub*, «te.
At*** of open can- Malting «now Culicida* 1,2
opy within conifer D
forest
*♦ Forest (closed Shores of Leigh Lake Culicida* ),3
canopy). Fir12 end String Lake D
spruce**
b. Snell needows
within forest
Desert A woodland
Oaks’ and Junipers
Desert (no trees) Culicida* E
Beside Big Thompson River 1,2
D
Meadow with scattered trees and shrubs Lake ce. I kn away 2,9 D
Forest (open canopy) Fir**. Sprue*’3, Aspen*. Beside Creek i 1.3 D
MAKE OF HABITAT LOCATION ELEVATION WEB SITES TERRAIN PLANT COMMUNITY BODIES OF WATER NUMEROUS DIPTERA TIME
Wind River Renee Wyoming, USA (Dubois) Culieidae H,E f
1. Arrow Mountain Abova timber* lint 3500 m Grate Gantls slopa Short harba Malting snow 2,2 D
2. Big Meadow* Sava r ai aeadows naar Gannat Faak 3000 n Shrubs s. Flat b, staap alopa a. Meadow, thick growth of shrubs (willows * 1). b. Conifer forast Beside Dinwoody Creak, Malting snow (especially in a) 4,9 m.d.e
3. Doubla Laka Savarai lakaa bttwaan Cannat Faak and Arrow Mountain 3000 n Shrubs Gantla and staap alopas Conifer forest (alternately closed and open canopy) Beside lakes. Malting snow M D
4. Gannat Tarn Abova tinber- lina 3500 b Shruba Gantla and staap stopaa Scattered short «1 b) willow11 shrubs 2.6 M.D.I
5. Ring Laka Bait of Whiskey Mountain 2000 a Shrubs Flat Scattered tlabar pinea1*, aage^ and other shrubs Beside laka 2,5 D.E
6. Whiskey Mountain1* Timbarlina 3500 b Shruba Staap slopa Thick arowth of willowl1 shrubs Beside snail stream created by aalting 1,2 D
•now
Table 1 – Description of habitats in which Diotyna and Malloe were studied. — Name of habitat: name
(underlined)| sometime abbreviated» of nearby distinctive geographical entity (city, mountain range,
etc.) used for name of habitat. When useful to designate areas within the habitat, these are listed and
numbered, but no underlined. — Location: State, country (Mx: Mexico; USA: United States of America).
In parenthesis, name of geographical entity in vicinity (“in” when habitat is within the entity). —
Elevation: Given to nearest 500 m. — Web sites: ”Buildings”, on outside walls of buildings. — Terrain
and Plant oomnunity: no comments for habitats within cities. Dominant trees and shrubs mentioned when
known. — Bodies of water and Numerous Diptera: noted when applicable. —*• Time: First, number of days;
second, estimate for total number of hours spent searching, collecting, and/or studying dictynids in
the habitat; M, D, E refer to times of day when habitats were visited; M, early morning (within few hr
before and after sunrise); D, mid-day; E, late afternoon and early evening (within few hr before and
after sunset).
Footnotes:
I: Quercue – 2: Opuntia – 3: Atriplex oaneeoeno – 4: Populus – 5: Acer negundo – 6: Juniperus deppeana
7 : Prosopis juliflora – 8 : Jugions • 9 : Artemisia – 10: Pinue aontorta – 11 : Salix – 12 : Abies –
13: Pioea – 14: Pinus flexipus – 15: see JACKSON (1976) for more complete description.
14 0
JACKSON
(1975) takes a similar view concerning the term “society” when applied to
animals in general. In this spirit» the term “social spider” will not be
defined here. Instead it will be used as a rather general expression» the
clarification of which is one of the ultimate goals toward which* this
study will hopefully contribute.
In the family Diotynidae there are approximately 350 described species
in 34 genera (CBAMBERLIN and GERTSCH» 1958; for a different classification»
see LEHTINEN, 1967), with species occuring in each of the major terrest-
rial biogeographical regions of the world. Numerous authors have provided
information (predominately qualitative) concerning the webs and other
aspects of the natural history of dictynids (BERLAND, 1916; BILLAUD ELLE,
1957; BRISTOWE, 1941, 1958; CHAMBERLIN and GERTSCH, 1958; CLYNE, 1969;
COMSTOCK, 1912; FORSTER and FORSTER, 1973; GERTSCH, 1949; KASTON, 1948;
LOCKET and MILLIDGE, 1951; MAIN, 1971; MASCORD, 1970; McKEOWN, 1963;
NIELSEN, 1931; WIEHLE, 1953; see above for references on M. gregalîs).
Based on this literature, it seems that the species in this study were
rather representative for the family.
The dictynids are generally small in body size, and rather much intra-
specific variation in body size was noted in this study (also see CHAMBER-
LIN and GERTSCH, 1958) • Females of M. trivittatus tend to be 7 mm in body
length, males, 5mm. MalZoe sp. (Lake Chapala) was of comparable size. Mm
dugeei, females tend to be 5 mm, males, 4mm. The remaining species tended
to be less than 5 mm in body length.
TYPES OF WEBS AND SOCIAL ORGANISATION
Twenty species were studied in nature, and four were studied in the
laboratory. From these data, three types of webs and three corresponding
types of social organisation were identified (table 2 and 3) •
Individual webs. Solitary species.
With a few exceptions that will be discussed later, solitary species
occupied their webs singly; and these webs were rarely fastened to other
webs. Typical individual webs are shown in fig. 1, 2 and 3. This type of
web is the simplest, and the other types of webs can be described as ela-
borations upon the design of individual webs.
Type of aocial organiaation Solitary Communal and territorial Communal and non-territorial
Type of web Individual Veb complex Communal veb
Componenta of web Mesh, neat Web units (mesh, neat) interstitial veb No veb units
Number of apidera per web1 One One or a small group Hundreds
Feeding One spider par prey One spider par pray, occasionally in small group Routinely in groups
Aggreaeion and cannibalism Tea Tea No
1Refera to web unit for communal and territorial apaciaa.
Table 2 — Characteristics correlated with different types of social orga
nization.
Dictyna and Mallos
14!
Figure J – Individual web of Af. nivene on dry stem of herbaceous plant.
Ms mesh. Large, tubular nest (N) at junction of smaller stem with
the primary stem (obscured by silk) • Toile individuelle de K. niveus
but une tige sèche de plante herbacée• M: réseau. Le nid (N)* large
et tubulaireê est à la jonction d’une petite tige sur la tige prin-
cipale {caché par la soie) •
Figure 2 – Very narrow individual web of Af. niveus on single dry stem of
herbaceous plant. Toile individuelle très étroite de M. niveus sur
une simple tige sèche de plante herbacée•
Figure 3 – Three individual webs (A,B,C) of Af. niveus built partially in
crevice on wall of building (W)^ Trois toiles individuelles (A,B,C)
de M. niveus construites partiellement sur une fente d’un mur de
mrnson.
JACKSON
Figure 4 – Diagram of web complex* Hs mesh. H: nest. I: interstitial web.
Schéma d’un complexe de toiles. H: réseau• N: nid• Is soie inters—
ticielle.
Figure 5 – Fart of web complex of D. atbopilosa built on herbaceous plant.
U: web unit. I: interstitial web. Partie d’un complexe de toiles de
D. albopilosa établi sur une plante herbacée. üs unité de toile. I:
soie intersticielle.
Figure 6 – Part of web complexe of M• trivittatus• Moss-covered rock (R)
under overhanging» mo s s-covered rock ledge (L), Note: extension
lines (E)t some with cross-lines (C) • Scale: ruler (lower right)
15 cm in length. Partie d’un corrplexe de toiles de H. trivittatus.
Rocher couvert de mousse (R) sous une saillie en surplomb couverte
de mousse (R) • Remarquez les prolongements de fils (E), certains
avec file transverses (C) . Echelle: la règle9 en bas à droite, mesure
JS cm•
Figure 7 – Communal web of M• gregalis on philodendron plant growing in
flower pot (P). Note fly carcasses (F) in web and leaf covered by
relatively little web (L) • Toile commune de M. gregalis sur un
“philodendron” poussant dans un pot (P). Remarquez les carcasses de
mouches (F) sur la toile et la feuille couverte d’une relativement
petite toile.
Dictyna and Mallos
1
JACKSON
144
Web complexes. Communal, territorial species.
One can visualize a web complex as the result of placing individual
webs in close proximity and connecting them by silk in the interstitial
area (fig. 4, 5 and 6). The number of units in a single veb complex is
highly variable. For each species, two was the minimum. Approximately
6 500 was the maximum for M• tvivittatus\ 19 for Dm calcarata; and 24 for
Dm albopitosa.
Communal webs. Communal, non-territorial species.
Mm gregaZis envelopes leaves, stems and sometimes whole branches of
trees (Acacia, Quercusf etc.) in Mexico in large sheet webs. As noted by
DIGUET (1909a, 1909b), the over-all appearance is rather like that of the
webs of tent caterpillars (fig. 7). The “surface sheet” (BURGESS, 1976)
is perforated with holes that lead into the interior of the web. Under
the sheet there are various sizes of “chambers”, similar to the nests of
other dictynids, and long tunnels, sometimes more than 10 cm in length.
Also there is a meshwork of “supporting lines” that connects the surface
sheet with the twigs, leaves, and other substrates beneath. The spiders
reside in the chambers much on the time, and egg sacs are placed here.
Territoriality.
WILSON*s (1975) definition of territory will be used: “an area occu-
pied more or less exclusively by an animal or group of animals by means
of repulsion through overt defense or advertisement.” Animal territories
may be defended against other species, conspecific individuals only, or
against only certain sex/age classes of conspecifics. In the dictynid
species that live in web complexes, web units seem to be territories that
large individuals defend against other individuals of comparable size.
Patterns of feeding, aggression and cannibalism are consistent with terri”*
torial behavior in these species and non-territorial behavior in Mm gre—
gaVLe, as will be discussed later.
WEB SITES
Considering the species in this study (table 3) and reports from the
literature for other species, a wide variety of web sites are used by
dictynid spiders; and there can be considerable intraspecific variability.
Also, the type of web sites used by solitary and communal species overlap.
The greatest variability was recorded for the species observed most exten-
sively in nature (table land 3), M, niveus and Mm trivittatus, suggesting
that greater variability for other species would be revealed if observa-
tion time were increased. In particular, we might expect more variability
for Mm gvegaVis in Mexico, since in the laboratory communal webs enveloped
stems and leaves of living plants, as well as numerous other objects such
as table tops, corners of the room, and light fixatures. Data from the
natural hatitats of this species are much needed.
SPECIES
SOCIAL ORGANISATION
DISTRIBUTION
HABITATS
WEB SITES
Hallo» duge»i bckir Solitary Southweste» USA, western and souths» Mexico Sen Anton Far^r Herbs (21)
Hallo» niveua O.P. Csmbridge Solitary Western USA, Mexico, Guatemala Guanajasto, Quaretaro, Chiracahua Mountains (1,2,3), Dinosaur, Rocky Mountain (1) Herbs (76), shrubs (29), trees (I), buildings (48)
Hallo» pallidue Bank* Solitary Western USA, northern Mexico Lake Chapala (2) f i Herbs (2)
Hallo» sp. Solitary * Lake Chapala (3,4) Herbs (4), shrubs (10)
Diotyna annexa Certsch 4 Chamberlin Solitary Texes, New Mexico, adjacent Mexico Juventinos Roses, Gila, Guadalupe Mountains Herbs (10), shrubs (12)
Diotyna annulip»» Blackwell Solitary Holarctic Wind River Range (5) Shrubs (10)
Diotyna ballon» Chamberlin Solitary Central USA as far west as Utah and Arisons, Mexico Rocky mountain (1) Herbs (4)
Diotyna ooloradenei» Chamberlin Solitary Canada, northern USA, Rocky Mountains end adjacent Great Plains Bandolier, Wind River Range (5) Shrubs (10)
Diotyna compléta Chamberlin 4 Certtch Solitary Western USA Wind River Range (1,4) H Shrubs (14)
Diotyna peon Chamberlin 4 Careach Solitary Southern Arirons and New Mexico, Mexico Chiracahua Mountains (5) Herbs (1)
Diotyna phylax Cetsch 4 Ivie Solitary y Canada, northern USA Grand Teton (3), Rocky Mountain (3) Herbs (2) shrubs (2) trees (36)
Diotyna tridentata Biahop 4 Rudeman Solitary Rocky Mountains south into Mexico Grand Teton (1,2,3), Rocky Mountain (2) Wind River Range (2,3) Herbs (9), shrubs (32)
Diotyna tuoeona Chamberlin Solitary Southwestern USA, Mexico Chiracahua Mountain (4) Herbs (1), shrubs (14)
Diotyna sp. Solitary Chiracahua Mountains (2) Herbs (3)
Diotyna ap. Solitary Querecho Plains Shrubs (20)
Diotyna ap. Solitary Wind River Range (6) Shrubs (10)
Diotyna ap. Solitary San Anton Falls Partially folded leaves of herbs (21)
Hallo» trivittatu» Banka Communal and territorial Western USA, northern Mexico Chiracahua Mountains (2,3,5,6) Flaming Gorge, Rocky Mountain 0,2) Metal culvert (ca.6 500) boulders (16), large roc rock ledges (85), trees buildings (1)
Diotyna albopilo»a Franganillo Communal and territorial Mexico, Cuba San Anton Falla Kerbs (77), buildings (1
Diotyna daloarata Banka Communal and territorial Waste» USA, Mexico Laka Chapala (1), San Migual de Aliende Buildings (128)
Table 3 * Dictynid species observed in nature* Distribution from CHAMBERLIN and 6ERTSCH (1958) • Habitats
refer to the specific locations at which found each species in this study* Numbers in parentheses refer
to areas within habitats (see table 1)* Number of occupied webs found at each type of web site listed in
parentheses.
KJ%

Dictyna and Mai to 8
JACKSON
A single occupied veb of AL niveiæ vas found on a dead stem of an
oak tree (table 3) in the Chiracahua Mountains (E. Turkey Creek)• However»
several empty webs» similar to this one» were found on dead stems of other
oak trees in the area» suggesting that although construction of webs on
trees may be les6 common than on shrubs and herbaceous plants» it is
nevertheless characteristic of this species.
The only other solitary species that was found on trees was Dm phylax
which built webs on green stems and needles of spruce ÇPioea) and fir
(Abies) trees. Perhaps this species has a preference for conifer trees»
but this needs further investigation.
Another possible example of web site specificity is Dictyna. sp. (San
Anton Falls)» all webs of vich were on the upper surface of green leaves.
In every case» each outer edge of the leaf parallel to the central axis
of the stem was rolled somewhat upward» and the webs were spun across the
basin made by the curvature of the leaf. Similar webs have been described
for other dictynids (e.g. BERLAND, 1916; WIEHLE, 1953).
With the exception of Dm phylax and Dictyna sp. (San Anton Falls),
when individual webs were located on plants they were especially prone to
be found on dry, dead stems. Of the 172 webs for which data were gathered
(see table 4 for sample ^sizes for each species, excluding D. phylax and
Dictyna sp.)» 81.98 Z were entirely on dry stems, 15.12Z were entirely on
green stems, and 2.91 Z were partially on green and partially on dry stems.
It would be valuable to investigate whether these spiders are actively
choosing dry stems for veb sites.
On occupied web (Arrow Mountain; Dm compléta)^ containing a male-female
pair, was fastened to a blade of grass and to two adjacent rocks. The grass
blade extended 6 cm above the ground, and the web was oriented vertically
along the grass and extended to the tip of the blade. The nest and the
spiders were in the lower part of the web beside a rock. This was the only
web of any species found on a blade of grass in this study.
Individual webs on shrubs, trees, and herbaceous plants were usually
constructed near the tips of the stems. The mean distance from the distal
end of the web to the stem tip was 0.9 cm (see table 4 for sample sizes
for each species) • The maxima were 30 cm for one Af. nivens web on a shrub
and 25 cm for a web of Dm phylax on a fir tree; 86.67Z of the webs extended
to within 0.5 cm of the stem tip.
The distance above the ground was rather variable, but generally it
was less for herbs than for shrubs (table 5) • Shrubs were generally taller
than herbs, and webs were usually constructed near the tops of herbs and
shrubs. Although trees were not searched at heights much greater than 2 m,
dictynid webs at Leigh Lake could be seen more than 3 m above the ground;
and it seems likely that dictynid webs on trees occur at even greater
distances above the ground.
GEOGRAPHICAL DISTRIBUTION AND HABITATS – .
Communal, territorial and solitary species were both found in tenpe-
rate as well as tropical regions. The only communal, non-territorial spe-
cies seems to be restricted to a tropical region with distinct rainy and
NUMBER OF WEBS
|^S MEASURED LENGTH WIDTH
ROUDNESS STEM DIAMETER SURFACE AREA
M. niveue A 29 4.5&2.0I 2.7Ü.20
M. niveue B * 1 12 4
M. niveue C’ 69 ‘ 12.3+5.47 2.611.29
M. pallidue 2 13, 8 2, 2
M. trivittatue 42 5.Oil.48 4.210.96
Malloe sp. (Lake Chapala) 8 12.6+3.70 3.4±2.56
D, annexa 16 10.9Î4.69 3.9±4.01
D. annulipee 10 9.4±3.17 2.041.41
D. oaloarata 26 2.5—1.57 1.810.89
D. coloradeneie 10 U.1Î3.14 4.012.63
D. compléta 8 6.5+1.19 3.510.76
D. phylax 8 9.5i4.00 3.4Î1.77
D. tridentata 31 8.5+2.89 4.312.87
D. tusoona 7 3.7Î1.50 1.410.79
Diotyna sp. (Querecho Plains) 11 11.112.85 3.511.13
o.olo.oo 0.610.10 no stem 12,1
2 0.3 2 , * 48.0
0.340.63 0.310.16 1.010,54 32.0
0, 0 0.1, 0.3 0, 0 21.0
0.010.00 0.910.16 no stern 21.0
0.310.46 0.310.26 0.910.35 42.8
0.411.03 0.310.20 0.910.57 42.5
0.110.32 0.210.16 1.2Î0.42 18.8
o.olo.oo 0.810.22 no .ten 4.5
0.911.60 0.410.18 0.710.48 44.4
0.610.52 0.510.07 0.710.46 22.7
0.140.35 0.440.17 1,. 510.54 32.3
0.310.46 0.510.28 1.110.51 36.5
o.olo.oo 0.410.13 0.710.49 5.2
0.310.47 0.3+0.15 1.210.41 38.9
Table 4 * Web characteristics. M, trivittatue and D. oaloavatax web units from web complexes (see table
2), all on relatively flat surfaces. All other species: solitary. D• phylaxx webs on conifer trees. M.
niveue A: on walls of buildings. A/, niveue B: on oak tree. All other individual webs: on herbs and shrubs.
Length, width, and depth defined in text. Roundness: width divided by length. Stem diameter at widest point
on primary stem (see text) within web. All measurements accurate to the nearest cm except stem diameter
(nearest mm). All measurements made on occupied webs. Means only provided for surface area (mean length x
mean width). Other characteristics: means * S.D., except for M. niveue B and D. pallidue for which actual
measurements are provided.
Oictyna and Mai to9
JACKSON
NUMBER OF WEBS DISTANCE
SPECIES WEBS SITES MEASURED
M. niveua Herbs 51 60 + ^ 1
Shrub6 18 112-43.9
Trees 1 145
M. pallidus Herbs 2 90, 60
MdlZoe sp* Herbs 1 60
(Lake Chapala) Shrubs 7 75±37.8
Dm annexa Herbs 10 66 ± 27.6
Shrubs 6 105±16.4
Dm annutipes Shrubs 10 99 ±28.5
Dm coZoradensie Shrubs 10 47 ±11.3
Dm compléta Shrub s 8 35 ±17.7
Dm phyZax Shrubs 2 130, 65
Trees 6 160124.5
Dm tridentata Herbs 7 52 ±10.4
Shrubs 24 105 ±26.5
Dm tucsona Herbs 1 35
Shrubs 6 55112.2
Dictyna sp* Shrubs 11 62124.9
(Querecho Plains)
Dictyna sp* Grass Blade (Wind River Range) 1 ‘ – ‘ .
Table 5 – Distances above the ground from proximal edge of web, solitary
species* Measured to nearest 5 cm, except for Dictyna sp* (Wind River
Range) which was measured to nearest 1 cm. When N ■ 1 or 2, actual distan-
ces instead of means provided*
Dictyna and Mallos
149
dry seasons. Generally there was considerable intraspecific variability
in the types of habitats occupied (see table 1 and 3)* M. niveus9 for
example, was found from desert habitats (Dinosaur) to relatively mesic
habitats (e.g.. Big Thompson Creek) » D. tuscona, another solitary species,
seems to be restricted to desert habitats, judging from collection sites
listed by CHAMBERLIN and GERTSCH (1958) and the fact that all those found
in this study were from desert habitats. None of the communal species were
found in desert habitats.
WEB SIZE AND GEOMETRY
Individual webs.
Webs built on stems of plants will be considered first. In these the
mesh is an array of silk lines with many relatively large gaps between
threads. The spatial relationship of threads has not been quantitatively
determined, but it would seem rather irregular, at least when compared to
a web such as that- of Artmeus diadematue Clerck (Araneidae) which has
consistent, regular symetry (WITT, REED and PEAKALL, 1968).
The shapes of webs are to a large extent correlated with the charac-
teristics of the stems around which they are spun. This contrasts with
the orb webs of araneid spiders, for exemple, in which shape is nearly
independent of the substrate on which webs are spun (BURGESS and WITT,
1976) • Of ten there was one stem with distinctly greater thickness (primary
stem) to which individual dictynid webs were fastened at numerous points.
Threads were frequently fastened to smaller side branches as well. The
primary stem usually was not much more than 1 mm in diameter (table 4) •
On shrubs there were always numerous stems present with greater diameter
than the primary stem. However, the primary stem was frequently the largest
stem on herbaceous plants.
The longest distance across the web (length) was more or less parallel
to the primary stem in almost every instance. The length of the web was
oriented most nearly vertically in 91.35Z of the 185 webs sampled (see
table 4 for sample sizes for each species), and most nearly horizontally
in 7.03Z. The longest axis of one web was not oriented clearly in either
the vertical or horizontal plane; and in another two, one axis was not
clearly of greater extent than the other. Width is defined as the second
greatest distance across the web on an axis perpendicular to the length.
When a third axis is imagined perpendicular to the plane containing the
length and width, the greatest distance across the web in this axis is
defined as the depth.
For most webs length was 10 to 12 cm, width was only a few centime-
ters, and depth was less than 1 cm (table 4). In other words, webs tended
to be two-dimensional in the sense that most of the silk lay in one plane.
In a few cases, depth was nearly as great as the width. However, even in
these cases, the web was two-dimensional in a sense. Lines of silk were
laid from the heavy central stem out to side stems; and in most webs this
was’ primarly to stems in a single plane approximately perpendicular to
the length and width of the web. In effect, these webs consisted of two
sections, each perpendicular to the other. Few if any threads tended to
JACKSON
go from one section to the other, except in the vicinity of the central
stem.
The vebs of M• niveuB built on walls of buildings were similar in
basic respects to those on vegetation. Each had a nest and a mesh with a
lattice-work appearance. However, these webs, set flat against the wall,
were almost entirely two-dimensional. The nest was always near the center
of the web. Usually the shape of the web approached that of a circle.
Compared to webs on vegetation (table A), length was less (t * 7.093,
P<0.001), perhaps reflecting a tendency to concentrate silk within a
shorter distance from the nest when the substrate is more uniform. On
vegetation, features of web site, such as the distance to branching stems,
may have a greater influence an web length. If this is the case, on might
also predict greater roundness of webs on walls; however, the differences
in table A were not significant (t-test)•
Measurements were not made on webs built across concavities of leaves
CDictyna sp., San Anton Falls), but these webs were estimated to be gene-
rally 3 cm long and 2 cm wide, usually approximately half the size of the
leaf.
In conclusion, individual webs of species in this study were rather
similar in size and structure, and geometry varied more with the nature
of the web site than with the species.
Web complexes.
In the Chiracahua Mountains there was an enormous web complex (esti-
mated surface area: 79 m2) in the metal culvert on East Turkey Creek,
estimated to coutain 6,500 occupied web units and 10,200 individuals of
Af. trivvttatue and covering almost the entire interior surface of the
culvert (JACKSON and SMITH, 1978). Web complexes of Dm catcarata and Dm
aZbopîZosa and other web complexes of Mm trivittatus were considerably
smaller, tending to be more or less 1 m2 in surface area.
Unlike the web complexes* of the other two species, those of Dm atbo—
piZosa were three-dimensional, since they were wrapped around leaves and
stems in dense growth of herbaceous plants (fig. 5). Detailed data concer-
ning these web complexes were not collected because of the difficulty of
dissecting the web units. However, most web complexes seemingly consisted
of a dozen or so units. Stem (0.67 i 0.59A cm) and leaf diameter (5.56 ±
1.120 cm) were measured for 19 plants that supported web complexes. Most
webs were wrapped around green leaves, although some were on dry ones.
These plants grew on the nearly vertical cliff6 beside San Anton Falls,
In some places, dirt had fallen away exposing roots of these plants, and
some web complexes were on the roots. Each web unit tended to be approxi-
mately 10 cm x 5 cm; however, the boundaries between units were often
difficult to distinguish. In some cases, an area of A00 cm2 or more was
almost completely covered with silk. More commonly, there was a patchwork
of areas alternatively covered and not covered by silk. The density of
silk in these webs was great in most cases, concealing the spiders and
the underlying vegetation. In some cases, careful examination revealed
nests; and these tended to be near the center of the web units.
Dictyna and Malloa
151
Communal webs.
Communal webs of M. gregatis in Mexico were variable in surface area
sometimes covering many square meters (DIGUET, 1909a, 1909b, 1915; BURGESS,
1976). The number of spiders per web varied greatly in nature and the
laboratory. Probably as many as 20,000 share single communal webs at times
in nature (JACKSON and SMITH, 1978).
EXTENSION LINES
Webs of M. trivittatu8 frequently had extension lines (fig. 6), which
are heavy lines composed of multiple threads that extend from the mesh to
an object some distance away. Of 92 sampled web units, 30.43Z had extension
lines. Excluding those without extension lines, there were 1.2 i 0.50 ex-
tension tines per web unit, each 18.6 t 9.62 cm in length. Similar lines
were seen in the communal webs of W. gregalie, extending from one communal
web or portion of a web to another or to an external object. Extension
lines were not found on webs of ather species. Potential functions of
these in prey capture have been proposed (JACKSON, 1978a).
DEBRIS AND PREY REMAINS IN WEBS
As noted by other authors, dictynid webs were often covered by con-
siderable amounts of dust and other debris. For example, at Grand Teton
(Climber*s Ranch) almost every D• tz*£dentata web contained seeds from
neighboring cottonwood trees. Webs built on walls of buildings were even
more prone to be covered by dust, sometimes causing these webs to be very
conspicuous (fig. 3). Dry, hollow carcasses of insects, probably prey
remains, were frequently found in the webs of virtually all species (JAC-
KSON, 1978a). In the communal webs of M• gregatie in the laboratory, great
numbers of fly carcasses accumulate (fig. 7), and there is no evidence
that the spiders ever remove them. Instead, new silk seems to be simply
added over the carcasses. Possibly in nature much of the debris from prey
is removed by beetles that live with the spiders in the webs (DIGUET,
1909a, 1909b, 1915; GERTSCH, 1949).
NESTS
The nest (retreat) is an area of more densely woven silk within the
mesh (fig. 1 and 4). Sometimes it was nearly opaque, but in other webs it
was only slightly more dense than the mesh’and not very conspicuous. Usu-
ally the shape was that of a hollow tube, with an opening at one or both
ends, which is apparently the most common shape for spider nests (McCOOK,
1889; JACKSON, 1978b; for other shapes of dictynid nests, see NIELSEN,
152
JACKSON
1931). Generally individual webs and web units within web complexes each
had a single nest. The spiders tended to occupy nests when not feeding,
spinning or otherwise active* Sometimes the margins of the entrance to’
nests (doors) were reinforced, forming a “gate” (WIEHLE, 1953)*
The size6 of ne6ts were not recorded, and this would have been quite
difficult in most cases because the boundaries of the nests were often
not distinct* It was noted, however, that most were approximately 1 cm in
length; but this tended to vary appreciably, ranging from not much larger
than the spider to ones exceeding 3 cm in length (fig* 1)*
In the case of Dm phyZax, when webs were found on conifer trees, the
ne8ts were nearly always (83Z) fastened to the primary stem and the need-
les* In the case of the Dictyna sp* (San Anton Falls) that built webs on
rolled leaves, the nest was always under one of the rolled edges of the
leaf* Considering only those webs built on shrubs and herbs for the remai-
ning solitary species, 18.29Z had nests inside or under dead leaves* (See
below for sample sizes for each species.) The leaves were dry, and usually
they were rolled or folded over to varying degrees* Nests were under dead
flowers In 17.07 Z of the webs,, In 48.78 Z of the webs, the nest was at a
fork in the primary stem (fig* 1); in 14.78Z, beside the primary stem but
not at a fork; and in the mesh but not next to a stem, leaf, or flower in
one web*
In the case of Af. niveu8 webs on walls of buildings, sometimes nests
were constructed partially or entirely inside cracks between bricks or in
other crevices (fig* 3)* Nests of Af* tvivittatus and Dm calcarata were
frequently founds partially inside crevices on bark of trees, rock ledges.,
walls of building, and so forth. Frequently nests were situated amongst
moss (fig. 6) or lichen on rocks or trees* Also nests were generally under
a mass of debris such as insect carcasses, regardless of whether they were
also inside a crevice or under moss or lichen* Other authors have noted
the tendency of dictynid nests to be situated in crevices or holes in the
substrate*
Considering 85 vertically oriented individual webs (Af* niveiiB, 33;
Maltoe sp.. Lake Chapala, 2; Dm annexa, 11; Dm coZoradensie 9 6; Dm phylax9
6; Dm tridentata9 15; Dm tuc8ona9 4; Dictyna sp*, Querecho plains, 8) on
herbaceous plants and shrubs, the nests of most were in the middle (54.12Z)
or upper (40.00Z) third of the web; and only 5.88 Z were in the lower
third*
It seems likely that nests function in protection from predators and
p ar as i to ids ; ^nd-various hypothetical mechanisms of this, proposed for.
vagabond spiders in the family SaZticidae (JACKSON, 1977b), would seem
applicable to the dictynids also. The location of the nest within the web
would seem to be an additional factor of importance for the dictynids* To
reach the nest, the predator would have to cross a sizable portion of the
mesh web, since nests were never at the periphery of the web. This proba-
bly delays the predators and provides the resident with early detection
of the predator’s approach* Placement of nests in concealed places, such
as in crevices, beside a stem, and so forth, might be expected to increase’
the predators9 problems in detecting the spider and capturing it once it
has been detected*
Number of webs per plant: • M, ni Hallos sp* D (Lake Chapala) amulipss D. compléta D. tridentata Dictyna sp. (Querecho Plains)
Two, only one occupied 2 0 0 0 4 2
Two, both occupied 4 2 2 0 0 0
Three, only one occupied 0 0 0 0 0 1
Three, only two occupied 1 0 0 6 1 4
Four, only two occupied 0 0 0 1 0 2
Distances between webs on same plant: Both occupied 74 Î45.I (5) 10, JO 30, 30 69*57.8 (7) 15 17 t 14.4 (6)
One occupied, other one not occupied 53 Î37.7 (4) r « – 70 i38.4 06) 27 ±6.1 (6) 26 t 17.0 (20)
Table 6 – Occurence of more than one web of the same species of solitary dictynid on single herbs and
shrubs. Occupied: containing spider of indicated species* Unoccupied dictynid webs on same plant assumed
to have been built by the indicated species* Distance: mean t S.D. (number measured), measured within 5 cm
of the most near edges. Actual measurements instead of means given when N » 2 or 1 • Touching webs excluded.
Plants with only one web or only unoccupied webs excluded.
* u»
Diatyna and Hallos
154
JACKSON
SPACING OF INDIVIDUAL WEBS
In most cases of individual webs built on shrubs and herbs» there
was only one dictynid web per plant* Exceptions occured in six species
(table 6). The distance to the nearest neighboring veb on the same plant
vas 44 ± 37*9 cm* There were no significant differences related to the
species involved or whether the neighboring veb vas occupied or not (see
table 6) • Often more than one veb of D. phylax vas found on the same tree»
but counting these vas not practical* The only cases in which individual
webs were found in conspicuous aggregations were some webs of Af. niveuB
on the walls of buildings in Guanajaato (fig* 3)» and the spacing of these
is discussed elsewhere (JACKSON and SMITH» 1978)*
CONNECTED INDIVIDUAL WEBS
When all solitary species are considered» 402 occupied webs were
observed in nature* A spider was in a veb that was connected by silk to
another veb occupied by a conspecific individual in only one instance*
this vas a pair of vebs on a vail in Guanajaato» each occupied by an im—
mature Af. nvveue* In another two cases » pairs of vebs on walls in Guanaja-
ato were connected to each other» but in each of these only one veb was
occupied* The only other observed case of connected vebs of a solitary
species vas ra female- 6f Vvctÿna sp* (Querecho Plains) » in a veb with a~
fev lines of silk connected to a similar unoccupied veb on the same shrub*
BILLAUD ELLE ( 1957) noted that when the vebs of D. civioa become especially
cluttered with debris and dust» the occupant may desert its veb and build
a new one connected to the old one* This is one possible explanation for
some of the cases in this study of occupied vebs connected to unoccupied
ones*
ISOLATED WEBS OF COMMUNAL# TERRITORIAL SPECIES
Although these species were usually found in veb complexes» occasio-
nally (68 webs) they were found in isolated vebs» defined a6 ones not
connected by silk to other vebs of conspecifics; i*e*»they were not parts
of veb complexes* Most (56) occupied isolated vebs were within 1 m of
other occupied isolated vebs or veb complexes* The other 12 were found
greater distances from other occupied vebs» although occupied veb comple-
xes were in the general area in each case*
In 29 small veb complexes only one occupied veb unit was located*
However» in some cases it vas difficult to discount the possibility that
some of the other veb units were occupied» since nests tended to be loca-
ted partially in crevices* Spiders possibly ran farther into the crevice
before I noticed them*
155
At Chapala 25.47Z of occupied veba on vails of buildings were isola-
ted webs, but each vas vithin 1 m of other vebs occupied by conspecifics*
At San Miguel de Allende 22 isolated vebs containing Dm calcarata vere
found on vails of buildings* Although no veb complexes vere found here,
each veb vas vithin 1 m of other occupied vebs*
Most of the Dm albopitoaa found at San Anton Falls vere in veb comp-
lexes* A few vere in isolated vebs, in close proximity of veb complexes,
and wrapped around the same type of vegetation* In nearby Cuernavaca 16
isolated vebs containing Dm albopilo8a vere found on vails of buildings,
each veb vithin 1 a of another occupied veb*
Isolated wehs of these species on vails of buildings, tree trunks,
and other relatively flat surfaces resembled the individual vebs of M.
niveus on vails of buildings* However, isolated vebs of Mm tnvittatus9
like veb units in veb complexes, tended to have extension lines* Also,
isolated vebs of each communal, territorial species differed from indivi-
dual vebs of solitary species in that they vere sometimes occupied by small
groups of spiders of varying sex/age classes (JACKSON and SMITH, 1978).
Unlike the majority of vebs of this species, four of the isolated
vebs of Mm tnirCttatuB vere located on branches and stems of trees* One
of these vas constructed flat against the underside of a living limb (12
cm in diameter) of an oak tree, approximately 1*5 m above the ground*
Three extension lines extended approximately 20 cm to a lower branch.
Another veb was on the underside of a 10mm dead stem on an oak tree* This
veb vas of particular interest because it had a latticework appearance,
not so different from that of Mm nCveus webs, rather than being flat
against the stem* Another two vebs vere found on dead stems .(diameter of
stems: 15 mm, 10 mm) of lodgepole pines: and these also had a latticework
appearance, similar to the vebs built by solitary species on stems. One
veb vas 33 cm long and 7 cm vide* The other was 19 cm x 14 cm* One vas lm
and the other was 2 m above the ground* These three vebs contrasted vith
the more common ones of this species in having much of the silk suspended
away from, rather than flat against, the substrate* Also, several other
vebs on rocks and tree trunks, both isolated ones and veb units complexes,
vere suspended to varying degrees* The manner in which this came about
vas that smaller diameter threads vere strung in a widely spaced manner
between several heavy extension lines, creating a veb vith a latticework
appearance (fig* 6).
GROUP SIZE IN M. GREGALIS
Although study of natural populations in Mexico will be needed in
order to determine the extent of variability in Af* gregalis> some obser-
vations from the laboratory are of interest. The spiders vere not confined,
but allowed to colonize new veb sites in the laboratory. Most spiders
vere in large communal vebs vith many other individuals* However, small
communal vebs containing only a few individuals vere frequently found;
and occasionally vebs containing single individuals vere seen* Also, indi-
vidual females and immatures experimentally isolated from communal vebs
and maintened individually in plastic cages survived indefinitely on a
diet of houseflies and/or Drooophilam
156
JACKSON
GROUPS OF SPIDERS SHARING INDIVIDUAL WEBS
There Were two special circumstances in which a group of spiders of a
solitary species were found sharing the same web: recently hatched imma-
tures in webs with females and joint occupation of webs by male-female
pairs. The pair could consist of an adult male with either an adult or
large subadult female. The subadults were most likely ones that would
mature at their next molt (JACKSON, 1978c).
Females of Af. niveus, D. tridentata % and Dictyna sp. (Querecho Plains)
were found with eggs in their webs. Usually eggs were situated* in and
around the nests» and often the female was inside the nest with her eggs.
As many as three egg sacs were found side-by-side in the same web. Dictyna
sp. (Querecho Plains) was the only species in with females were found with
their recently hatched progeny. In some cases there were tiny spiderlings
clustered around the egg sacs in webs containing females» and sometimes
the female was surrounded as well. In other cases» tiny spiderlings» appa-
rently first instar (terminology: WHITCOMB, 1973), were found scattered
throughout the web.
SYMPATRY AMONG DICTYNID SPECIES
Many of thé special in this study were sympa trie with each other
(table 7) • Since I stayed only 2 or 3 hr in some habitats (table 1) these
observations are only a minimal estimate of the amount of sympatry that
occurs. Strict correlations between social organisation, habitats, and
web sites did not occur.
HABITAT
Chiracahua Mountains
Cave Creek Canyon
East Turkey Creek
Rustler*8 Park
SYMPATRIC SPECIES
Mallo8 niveus, Hallos trivittatus 9 Dictyna sp.
Hallo8 niveus, Hallos trivittatus
Hallos trivittatus, Dictyna peon
Grand Teton National Park,
Leigh Lake Dictyna phylax9 Dictyna tridentata
Rocky Mountain
Big Thompson Canyon
Eastes Park
Hallos niveus 9 Hallos trivittatus, Dictyna bellans
Hallos trivittatus, Dictyna tridentata
Wind River Range, Ring
Lake
San Anton Falls
Dictyna armulipes, Dictyna coloradensis
Dictyna albopilosa9 Hallos dugesi9 Dictyna sp.
Table 7 “ Sympatry of Dictynid species.
157
The communai and territorial species Af. trivittatus was sympatric
with several solitary species. In each case the species were sometimes
found within less than In of each other. For example, once at East Turkey
Creek a Af. trivittatus was found in an isolated web on an exposed root of
a large shrub (Fraxinus valentia) with a M. niveus in a web less than 1 m
away on a stem of the same plant; and the large web complex in the culvert
was only a few metters away. Although Af. trivittatus generally adopted
relatively flat surfaces as web sites and the sympatric solitary species
generally were found on stems of plants, web site separation by these
species was not absolute (table 3) •
The three sympatric species at San Anton Falls were each found within
1 m of each of the others. The Dictyna sp. that built webs on partially
folded leaves was on a different type of vegetation from the other two
species. However, M• dugesi and D. albopilosa shared the same plants, and
sometimes the two species had lines of silk connecting their webs. This
was the closest physical association between the two dictynid species
found in this study.
The Dictyna sp. at Cave Creek Canyon was found on the same type of
herbaceous plants as Af. niveus and in one case within 2 m of a web occup-
ied by Af. niveua. The three species at Big Thompson Creek were each found
within the same few square meters. At Leigh Lake Dm tridentata and Dm phy-
tax did not overlap in web sites since the former were on shrubs and the
latter were on trees. Dm tridentata were in small clearings, several meters
from the nearest Dm phylax in the surrounding forest. However, in other
habitats, a few D• phylax were found on herbs and shrubs (table 3), indi-
cating that web site specificity was not absolute. Dm annulipes and Dm
coloradensis were found on the same types of plants, sometimes within 1 m
of each other at Bing Lake, but never on the same individual plant.
These observations raise the question of how sympatric dictynid
species avoid competitive exclusion. Although web site specificity may
play a role in some cases, the great intraspecific variability found for
some species cautions against hasty conclusions. Future long-term studies
should investigate other factors such as phenology and prey selection; but
most importantly, studies are needed to clarify the degree of competition
that occurs between coexisting species (see WIENS, 1977).
LONGEVITY OF WEBS
We do not have data concerning exactly how long webs are used by die-
tynids in nature, but dictynid webs seem to be relatively permanent stru-
ctures compared to the orb webs of araneids, for example (see WITT, REED,
and PEAKALL, 1968). The possible selection of dead stems as web sites by
Dictyna and Hallos species may be related to the relatively long endurance
of their webs. Perhaps a growing, green stem is a less suitable web site
because it requires rather much maintenance concurrent with growth of the
plant. Also, a web on a green stem may suffer from greater risks of inad-
vertent destruction or damage by feeding herbivores.
JACKSON
Web complexes may have greater longevity than individual webs. In
some web complexes of each species, the mesh web was quite dense, comple-
tely concealing the substrate beneath; but webs of solitary species were
generally less dense. In many cases the term “sheet web” is more appropri-
ate for web units than “mesh web”. Since the web complex in the culvert
at East Turkey Creek had been seen by other people several years earlier
(V.D. ROTH, personal communication), it seems likely that veb units in
some veb complexes are used by successive generations of spiders and that
new silk is continually added, gradually incrasing the density of silk in
the veb. It is noteworthy in this connection that juvenile D• civioa, a
species that occurs in aggregations of individual webs on vails of buil-
dings, will use abandoned vebs of adult for at least a few weeks after
hatching (BILLAUDELLE, 1957).
In the laboratory, populations of Af. gregaZîs have lived in the same
communal vebs for several years, to which they continually add fresh silk.
Although DIGUET (1909a) made reference to Af. gregaZi-s adults abandoning
their communal webs at the end of the rainy season, so few field observa-
tions have been carried out with this species that its life history in
Mexico is quite unclear at this time.
GENERAL DISCUSSION
The distinction between a web conplex and an individual web seems not.
so enormous. If we assume that the species which build veb complexes
evolved from species that built individual webs, the most important steps
would seem to be a tendency to place webs in close proximity and a certain
degree of tolerance for conspecific individuals in touching webs. If we
assume that Af. gregaZie evolved from a species that constructed veb comp-
lexes, perhaps similar to those of D. atbopi-Zosa on vegetation, the neces-
sary steps would seem to be incrassed tolerance of conspecific individu-
als in close proximity and elimination of tendencies to confine spinning
behavior within a single web unit. The result would be a large sheet web,
with neither boundaries nor interstitial web areas, perhaps not so diffe-
rent from a Af. gregaZie communal web. More information concerning the
manner in which each type of dictynid constructs its webs would be very
valuable.
Since social organisation was found to vary widely within a single
group of closely related species, the results of this study are consistent
with the hypothesis that social organisation is among the most evolutio-
narily labile traits of animal species (WILSON^ 1975). Similar wide vari-
ation within groups of related species occurs in other spider families
(e.g., see KRAFFT, 1970).
Generally spiders live in an aggregation for a period after hatching.
The duration of this period varies from species to species, but the dura-
tion of the postembryo stage and at least part of the first instar seems
to be most common. The potential significance of this phenomenon in the
evolution of social spiders has been considered by BERLAND (1928), KRAFFT
(1970), and KULLMANN (1968, 1972, 1975). The tendency of the early instars
to aggregate may have been a behavioral substrate on which natural selec-
Diotyna and Mallos
159
tion has acted during the evolution of spider sociality* In some species9
the spider lings remain together with the mother for several instars;
maternal care, including feeding of the spiderlings by regurgitation, may
occur; and the spiders disperse before maturing. KULLMANN (19689 1972)
referred to these as “periodic-social” species, and he suggested that
“permanent social” species, in which the adults remain together, evolved
by extending this trend into adult life*
One of the important future tasks will be to determine how appropriate
this hypothesis is for the dictynids* Spiderlings of only one solitary
species have been observed-in this study; and there was no evidence of
prolonged aggregation since all were apparently first instar spiderlings*
Since BRI STOWE (1958) noted that immatures of some solitary dictynids
remain in the maternal web for prolonged periods, further investigation
of this question would be valuable* BRISTOWE reported that the spiderlings
fed on insects in the web; however» regurgitation-feeding has not been
reported in dictynids*
Since web_ units of the communal and territorial species generally
contained either one spider or a small group consisting of individuals of
varying sex/age classes, it seems unlikely that siblings of single broods
remain together for prolonged periods, in the same web unit, although
they may remain in the same web complex. Hypothetically, some spiderlings
eventually build new web units within the web complex of origin; others
disperse away from the web complex; and still others enter existing web
units in which they are tolerated if they do not overlap in size with
resident spiders.
More information concerning the Australian dictynids in the genus
Ixeuticua would be valuable for comparison with Dictyna and Mallos • Some
species live in individual webs* From MAINfs (1971) brief descriptions,
it seems that juveniles of X. candiduQ build web complexes on vegetation
around the mother’s web; but they disperse and live in individual webs
when mature* Other species live on vegetation and in caves (McKEOWN, 1963)
in webs that may resemble the communal webs of M* gregalis.
The family Amaurobiidae is closely related to the Dictynidae, and at
times the two families have been treated as a single family* It is note-
worthy that webs of some Australian Amaurobiids may be similar to the
communal webs of M. gvegalie (BERLAND, 1932; GERTSCH, 1949; RAINBOW, 1905).
It has frequently been argued that the adaptative significance of
territorial behaviour in animals is related to the territorial individual
gaining exclusive or nearly exclusive access to a set of resources within
the defended area (see BROWN, 1975; WILSON, 1975)» A web unit within a
web complex might contain a number of resources the defense of which
would be optimal for the resident spiders* The mesh and especially the
nest might be an important resource related to protection from predators*
Also, males may treat females within web units as resources that they
defend against other males* However, the most important factor may be that
the mesh is a prey capturing device. The web unit can be viewed as a food
resource containing the prey made available by means of the mesh*
A question on which future ecological studies should focus concerns
the factors which favor territorial behavior in one set of communal spe-
cies and sharing of the web and prey in another species, Af. gregalis•
JACKSON
We can now return to the question raised at the beginning of this
paper: what are the characteristics of v,social spiders”?A useful approach
to this question is the set of three criteria proposed by KULIMANN (1968,
1972): tolerance, interattraction, and cooperation. Tolerance refers to the
fact that social spiders are not very cannibalistic or aggressive toward
each other. Interattraction (DARCHEN, 1965) refers to the fact that social
spiders occur in groups because they are attracted to each other in some
sense, rather than because they are attracted in common to some factor in
the environment* Although cooperation is a difficult concept to define,
it may be the most important critérium* As WILSON (1975) pointed out, this
concept repeatedly turns up either explicitly or implicitly in definitions
of sociability; and it seems to be close to the essence of what is inte-
resting about animals that ve think of as social* The intuitive idea is
that the cooperative individual does things that are somehow for the bene-
fit of other individuals in the society (WILSON, 1975). Also a certain
degree of coordination of activities would seem to be part of the concept
(SUDD, 1963). Comparative studies in this laboratory are presently inves-
tigating dictynid spiders with respect to KULLMANN*s three criteria*
If one had to choose a single characteristic of spiders that is most
important for understanding adaptation and diversity in this group, it
would probably be silk production* Spiders are perhaps largely the product
of an evolutionary lineage entering an adaptative zone (SIMPSON, 1953)
that is somehow defined by the use of silk* Vagabond spiders use silk for
construction of nests, enclosure of eggs, sperm induction, courtship, etc*
When it comes to web-building spiders, any reasonably complete understan-
ding of these specie^ would seem to demand a thorough knowledge of their
8ilk-related behavior and the characteristics of their webs* In the pre-
sent work with dictynids, web characteristics have proven integral to
understanding social organization* Three basic types of social organiza-
tion occur, with three corresponding types of webs.
Acknowledgements
For his assistance during all phases of this work, very special
thanks are extended to Peter N. WITT. Wesley BURGESS, Sandra SMITE and
Zuleyma HÀLPIN provided valuable discussions and comments on the manuscript.
I thank Mary Catharine VICK, Carol WILLARD, and Rubenia DANIELS for help
in the preparation of the manuscript* Special thanks are extended to
Willis J* GERTSCH for valuable discussions and assistance in the identi-
fication of spiders* I also thank Norman PLATNICR and Vincent ROTH for
help in identification of spiders. For their assistance in the field,
thanks are extended to Steve JOHNSON, Art METCAFF, David SMITH, Vincent
ROTH and especially Charles GRISWOLD and Steve JACKSON* For their assis-
tance in the laboratory, thanks go to Lennell ALLEN and Mabel SCARBORO*
The assistance of Southwestern Research Station of the American Museum of
Natural History and the U* S* National Park Service is gratefully acknow-
ledged* This research was supported in part by the N* C. Division of
Mental Health Service, Research Section and by a N* S* F* grant ko P*N*
WITT.
Dictyna and Mal to8
161
REFERENCES
BEER, C.G., 1977 – What is a display 7 — Amer. Zool. t 17 : 155 – 165.
BERLAND, J., 1916 – Note préliminaire sur le cribellum et le calamistrum
des Araignées cribellates et sur les moeurs de ces Araignées. —
Arch. Zool. expér. gén. * 55 s 53 – 66.
BERLAND, L., 1913 – Utilisation pour la capture des Mouches, des nids de
l’Araignée mexicaine Coenothele gregalis E. Simon. *— Bull. Mus.
hist, nat.j 1913 : 432-433.
BERLAND, L., 1928 -La répartition géographique des Araignées sociales. —
C.R. Soc. biogéogr., 37 : 33 -36.
BILLAUDELLE, H., 1957 – Zur Biologie des Mauerspinne Dictyna civica (H.
Luc.) (Dictynidae, Araneida) • — Z. Angew. Entomol., 41 : 475-512.
BLANKER R., 1972 – Untersuchungen zur Okophysiologie und flkethologie von
Cyrtophora citricola Forskal (Araneae, Araneidae) in Andalusien. —
Forma et Functio9 5 s 125 – 206.
BRACH, V., 1975 -The biology of the social spider Anelosimus eximus (Ara-
neae: Theridiidae) • — Bull. S. California Acad. Sci., 74 : 37-41.
BRACH, V., 1977 – Anelosimus studiosus (Araneae: Theridiidae) and the
evolution of quasisociality in theridiid spiders. — Evolution, 31:
154 – 161.
BRISTOWE, W.S., 1941 – The comity of spiders, vol. II.——Bay Society9-
London.
BRISTOWE, W.S., 1958 — The world of spiders. — Collins, London.
BROWN, J.L., 1975 – The evolution of behavior. ~ Norton, New York.
BURGESS, J.W., 1976 – Social spiders. — Sci. Amer., 234 : 100- 106.
BURGESS, JJW., 1978 – Social behavior in group-living spider species. —
Symp. Zool. Soc. London, in press.
BURGESS, J.W. & WITT, P.N., 1976- Spider webs: design and engineering. —
Interdispl. Sci. Rev., 1 : 322-335.
BUSKIRK, R.E., 1975 – Aggressive display and orb defense in a colonial
spider. Metabus gravidus. — Anim. Behav. , 23 : 560-567.
CHAMBERLIN, JU3U 6 GERTSCH, W.J., 1958 – The spider family Dictynidae in
America north of Mexico. — BUZZ. Amer. Mus. Nat. Rist., 116: 1-152.
CHAUVIN, R. & DENIS, J., 1964 – Une nouvelle espèce d’Araignée sociale,
Agelena consociata Denis. — Biol. Gabonica9 1 : 93 – 99.
CLYNE, D., 1969 – A guide to Australian spiders. — Nelson, Melbourne.
COMSTOCK, J.H., 1912 – The spider book. — Doubleday, New York.
DARCHEN, R., 1965 – Ethologie dvune araignée sociale, Agelena consociata
Denis. — Biol. Gabonica9 2 : 117 – 146.
DARCHEN, R., 1968 – Ethologie dfAchaearanea disparata Denis, Araneae,
Theridiidae, araignée sociale du Gabon. — Biol. Gabonica9 4: 5-25.
162
JACKSON
DARCHEN, R., 1973 – L’Ecologie d’une araignée sociale (Agelena consociata
D.) à la lumière de quelques expériences de laboratoire* — Insectes
Sociaux, 20 : 379-384,
DARCHEN, R., 1975 – Les communications sociales chez Agelena consociata D,
(Aranéide, Labidognathe) • — C.R. Acad. Sci., Paris, 281 : 575-578,
DARCHEN, R,, 1977 – La fondation de nouvelles colonies d’Agelena conso-
ciata et d’Agelena republicans, araignées sociales du Gabon. Prob-
lèmes êco-éthologiques. Pp. 20-39, in: Troisième réunion des arach-
nologistes d’expression française (* C. R. Col. Arachnologie Fr.),
Les Eyzies, 1976. *
DIGUET, L., 1909a – Sur l’araignée mosquero, — C» R. Acad» Sci», Parie,
148 : 735 – 736.
DIGUET, L., 1909b – Le mosquero. Nid d’Araignée employé dans certaines
régions du Mexique comme piège è mouches. — Bull. Soc» Acclim.
France, 56 : 368 -375,
DIGUET, L., 1915 – Nouvelles observations sur le mosquero ou nid d’Araig-
nées sociales ëmployê comme piège a mouches dans certaines localités
du Mexique. — Bull» Soc. Acclim» France, 62 : 240-249.
FORSTER, R.R. & FORSTER, L.M., 1973 – New Zealand spiders. — Collins,
Auckland.
GERTSCH, W.J., 1949 – American spiders. — Van Nostrand, Princeton.
JACKSON, R.R., 1976 – The evolution of courtship and mating tactics in a
jumping spider Phidippus johnsoni (Araneae, Salticidae). —Ph. D.
Thesis, University of California, Berkeley.
JACKSON, R.R., 1977 – Predation as a selection factor in the mating stra-
tegy of the jumping spider Phidippus johnsoni (Salticidae, Araneae).
— Psyche, 83 : 243-255.
JACKSON, R.R,, 1978a – Comparative studies of Dictyna and Mallos (Araneae,
_____ Dictynidae): III. Prey and feeding behavior. — In prep.
JACKSON, R.R., 1978b – Nests of Phidippus johnsoni (Araneae, Salticidae):
characteristics, pattern of occupation and function. —- Tn Review.
JACKSON, R.R., 1978c – Web sharing by males and females of dictynid spi-
ders. — Bull. Brit. Arachn. Soc., in press.
JACKSON, R.R. & SMITH, S.E., 1978 – Aggregations of Mallos and Dictyna
(Araneae, Dictynidae): population characteristics. — In prep.
KASTON, B.J., 1948 – Spiders of Connecticut. — Bull. Connecticut Geol.
Bat. Hist. Survey, 70 : 1 -874.
KRAFFT, B., 1969 – Various aspects of the biology of Agelena consociata
Denis when bred in the laboratory. — Amer. Zool., 9 : 201 -210.
KRAFFT, B., 1970a – Contribution â la biologie et à l’éthologie d’Agelena
consociata Denis (Araignée sociale du Gabon). Première partie.——-
Biol. Gdbonica, 6 : 197 -301.
KRAFFT, B., 1970b – Contribution â la biologie et à l’éthologie d’Agelena
consociata Denis (Araignée sociale du Gabon). Deuxième partie. —
Biol. Gdbonica, 6 : 307 – 369.
Dictyna and Halloa
63
KRAFFT, B., 1971 – Contribution à la biologie et â l’éthologie d’Agelena
consociata Denis (Araignée sociale du Gabon). Troisième partie.
Etude expérimentale de certains phénomènes sociaux. — Biol• Gobonica,
y : 3-56.
KRAFFT, B., 1975 -La tolérance réciproque chez l’araignée sociale Agelena
consociata Denis. — Froc. 6th Internat. Araah. Congr., 1974 : 107-
112.
KULLMANN, E., 1968 – Soziale Phaenomene bei Spinnen. — Ineectee Sociaux,
15 : 289-297.
KULLMANN, E., 1969 – Beobachtungen zum Sozialverhalten von Stegodyphus
sarasinorum Karsch (Araneae, Eresidae)• — Bull. Hue. Nat. Eist. ,
(1) 41, suppl. 1 : 76-81.
KULLMANN, E», 1972 – Evolution of social behavior in spiders (Araneae;
Eresidae and Theridiidae) • — Amer. Zool. , 12 : 419-426.
KULLMANN, E., NAWABI, S. & ZIMMERMANN, W., 1972 – Neue Ergebnisse zur
Brutbiologie cribellater Spinnen aus Afghanistan und der Serengeti
(Araneae, Eresidae). — Z. Kolner Zoo, 14 : 87-108.
KULLMANN, E. & ZIMMERMANN, W., 1975 – Regurgitationsfutterungen als Dest-
andteil der Brutfursorge bei Haubennetz und Rohrenspinnen (Araneae,
Theridiidae und Eresidae). — Proc. 6 th Internat. Arach. Congr.,
1974 : 120- 124.
LEHTINEN, 1967 – Classification of the cribellatespiders and some
allied families, with notes on the evolution of the suborder Araneo-
morpha. —Ann. Zool. Penn., 4 : 199-468.
LOCKET, G.H. & MILL EDGE, A.F., 1951 – British spiders, vol. 1. — Bay
Society, London•
LUBIN, T.D., 1974 – Adaptative advantages and the evolution of colony
formation in Cyrtophora (Araneae: Araneidae) • —Zool. J. Linn. Soc. 9
54 : 321 -339.
MAIN, B.Y., 1971 – The common “colonial” spider Ixeuticus candidus (Koch)
and its synonyms (Dictynidae: Araneae). — J. Boy. Soc. W. Australia,
54 : 119-120.
MASCORD, R., 1970 – Australian spiders in coulour. – Tuttle, ^Butland,
Vermont•
McCOOK, H., 1889 – American spiders and their spinningwork, vol. I. —
Philadelphia.
McKEOWN, K.C., 1936 – Spider wonders of Australia. — Angus & Bohertson,
Sydney.
NIELSEN, R., 1931 – The biology of spiders, vol. I. — Levin and Hunskgar
ard, Copenhagen.
PAIN, G., 1964 – Premières observations sur une espèce nouvelle d’Araignées
sociales, Agelena consociata Denis. — Biol• Gabonica, 1 : 47 -58.
PEAKALL, D.B., 1968 – The spider’s dilemma. — New Scientist, 4 : 28 -29.
RAINBOW, W.J., 1905 – Studies in Australian Araneidea. No 4. — Bee•
Austral. Hue6: 9-12.
SEMICHON, L«, 1910- Observations sur une araignée mexicaine transportée
en France. — Bull• Soc. Entomol. France, 1910 : 338 -340.
1 64
JACKSON
SIMON, E.f 1909 – Sur l’Araignée mosquero. C, R. Acad• Soi., Parie,
148 : 736-737.
SIMPSON, G.G., 1953 – The major features of evolution. —Columbia univer-
sity Press$ New York.
SUDD, J., 1963 – How insects work in groups. — Discovery : 15-19.
WHITCOMB, W.H., 1978 – Ontogeny of North American wolf spiders. — Symp.
Zool• Socm LondonM in press.
WIEHLE, H., 1953 — Spinnentiere oder Arachnoidea (Araneae) • IX: Orthogna-
tha, Cribellatae, Haplogynae, Entelegynae (Pholcidae, Zodariidae,
Oxyopidae, Mimetidae, Nesticidae). in : DAHL, F. (ed.) Die Tierwelt
Deutscblands. — Fischer, Iena.
WIENS, J.A., 1977 — On competition and variable environments. — Amer•
Soi. , 65 : 590-597.
WILSON, E.O., 1971 – The insect societies. — Belknap, Cambridge, Massa-
chusette.
WILSON, E.O., 1975 – Sociobiology. — BeTknap% Cambridge t Massachusetts*
WITT, P.N., HEED, C.F. & PEAKALL, D.B., 1968 – A spider’s web. —Springer
Verlag> New York•