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REPRINTED FROM
SOCIETY FOR NEUROSCIENCE ABSTRACTS
VOL. 4, NOVEMBER 1978

PATTERNS OF BEHAVIOR IN SOLITARY AND COMMUNAL SPIDERS.

Peter N.
Witt, N. C. Mental Health Research, Raleigh, N. C. 27611.
When speed and amount of food uptake, web-building activity
throughout the day, movement characteristics, and production of
offspring in the laboratory and outdoors are compared between the
solitary orb web builders like Araneus diadematus Cl. (A. d.) and
colonial spiders Mallos gregalis Simon (M. g.) from Mexico, dif-
ferent forms of behavior emerge. While young A. diadematus fe-
males (mean weight 55 mg) readily consumed radioactively labeled
glucose (injected into a live fly), close to 100% in 120 min, a
group of M. gregalis of the same average body weight took more
than 1,000 min to ingest the same amount. The latter animals
followed a pattern of approaching and leaving the prey repeatedly
in 24 hrs. Increasing activity of hungry individuals together
with movement to fly-catching surface of the three dimensional
web apparently helps M. gregalis to distribute food evenly through-
out a 20 member colony. Time-lapse movies and animal counts on
different web parts provide data supporting such observations.
The relatively greater fly-holding capacity of the Mallos web,
measured by Jackson (Beh. Ecol. Sociobiol., 1978), makes it pos-
sible for the slower spiders to eventually eat as much of the
trapped prey as A. diadematus without attack and wrapping. Slow
movements across the web with frequent meetings in M. gregalis
seem to have exploratory as well as communication function. In
contrast, A. diadematus moves in the laboratory only for web re-
newal or when prey has hit. No evidence for recycling of silk
could be found in M. gregalis using radioactive labeling techni-
ques, while Peakall (J. exp. Zool., 1971) has shown that A. dia-
dematus digests and incorporates 98% of old silk into daily re-
newed webs. Under controlled, steady laboratory conditions M.
gregalis raise offspring all year round; in the changing climate
of Mexico, Burgess (dissertation, 1978) found a seasonal rhythm
in appearance of spiderlings. A. diadematus maintain circadian
and annual rhythms even in a constant environment. — It is hypo-
thesized that in spiders a relatively flexible, environment-de-
pendent behavior is associated with communal living, while pre-
dominantly innate patterns of rigid behavior characterize the
solitary life style. (Supported by NSF grant No. BNS-75-09915-
02A).