THE SHEET WEB AS A TRANSDUCER, MODIFYING VIBRATION SIGNALS IN SOCIAL SPIDER…
NEUROSCIENCE ABSTRACTS

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REPRINTED FROM: NEUROSCIENCE ABSTRACTS
SOCIETY FOR NEUROSCIENCE, 5TH ANNUAL MEETING
NEW YORK CITY 1975. PRINTED IN THE U.S.A.
THE SHEET WEB AS A TRANSDUCER, MODIFYING VIBRATION SIGNALS IN SOCIAL
SPIDER COLONIES OF MALLOS GREGALIS« J. W. Burgess* (SPON: P. N. WITT).
North Carolina Mental Health Division, Raleigh, N. C. 27611.
The sheet web of Mallos gregalis tailors vibrations to fit the colony*8
behavior patterns. In a social context, it is important to locate
acceptable prey on the web and differentiate it from other colony members.
B. Krafft has identified close-range chemotactic signals Inhibiting pre-
dation in social spiders (Agelena consociata)« Mallos gregalis on three-
dimensional sheet-webs in nature and the laboratory orient to struggling
prey at distances over 10 cm, but do not orient to web vibrations caused
by colony members% Electronically generated vibration transmitted through
the web to a magnetic pick-up shows that transmission is limited to a band
between 50-500Hz (measured on an oscilloscope), and sine-wave vibration
is amplified at peaks within that band. Pure tones introduced on the web
over a range of 10-100,000Hz elicit predation behavior (orientation and
directional movement) only within the 50-500Hz band, proportional to the
web-response curve. Measured on the web, vibration of a trapped housefly
is prominent within the web-response band, recorded on a Brtiel and Kjaer
audio analyzer, while this vibration measured off web is spread over a
wide frequency range, from 50-5000Hz. The fly*s vibration is modified by
the web into a signal to which spiders readily respond, but other spiders
moving on the web do not generate measurable vibrations within this band.
Since intra-colony predation is not seen, it is suggested that the filter/
amplification characteristics of the web act to stimulate fly predation,
while inhibiting inter-spider predation. (Supported by NSF Grant GB25274
to P. N. Witt.)