20th International Congress of Arachnology

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DENVER MUSEUM OF NATURE & SCIENCE REPORTS | No. 3, July 2, 2016
compensated the lack of wind detectors (trichobothria)
in our study.
Keywords: filiform hairs, predatory behavior, sensory
organ, vibration, wind detector
Student - oral presentation
Social networks as a metric of sociality in
spiders
*Lucia C. Neco¹, Nicolas Châline¹, Charbel El-Hani²,
Hilton Japyassú²
¹Institute of Psychology, University of Sao Paulo, SP,
Brazil; ²Institute of Biology, Federal University of
Bahia, BA, Brazil
Sociality encompasses a wide range of social pheno-
types and complexities. Beyond Wilson’s eusociality
threshold, based on reproductive division of labor,
generation overlap and alloparental care, and other
qualitative measures, recent papers have proposed to
measure sociality quantitatively. Indeed, quantitative
metrics that take into account various characteristics
of sociality seem to constitute more useful tools for
comparative studies of social behavior. Social network
analysis (SNA) is currently used as a means to describe
social structures in animals, and the network structure
characteristics can be compared between groups of
different composition and even species. Social spiders
are good models to study social behavior because
they present different levels of sociality in different
taxonomic levels. In this context, we used association
data between individuals to develop a social network
approach in Anelosimus eximius colonies and describe
their structure. In addition, since division of labor is
an important feature of eusociality, one of the major
transitions in evolution, we tested for the existence of
clusters in their social organization through different
social contexts. Anelosimus eximius doesn’t seem to
present consistent clusters in the colony across contexts,
but specialists could be identified during the perfor-
mance of specific tasks in the colony.
Keywords: sociality, Anelosimus, division of labor,
metrics
Poster presentation
Preliminary description of defensive silk in
Latrodectus hesperus
David R. Nelsen1, Chris Hansen2 , Aaron G. Corbit 1
1PO Box 370, Department of Biology and Allied
health, Southern Adventist University, Collegedale,
TN 37315, USA; 2PO Box 370, Department of Physics
and Engineering, Southern Adventist University, Col-
legedale, TN 37315, USA
Numerous studies have looked at the properties of
spider silk from an ecological perspective. Of these
studies, most have looked at how spiders use silk in a
predatory context (prey capture) while comparatively
few have looked at defensive silk use, with most of
these focused on stabilimenta in orb weavers. To date,
two studies have been published on defensive silk use
in Western black widow spiders, but none have focused
on the physical characteristics of the silk. In this study,
we present a preliminary description of the physical
properties of defensive silk produced by Latrodectus
hesperus which, when sufficiently threatened, actively
tries to apply this silk to its attacker. We found that,
unlike the sticky globules used for ensnaring prey
items which are small (median 0.004 nL; range
0.001–0.008), these viscous globules are often rela-
tively large (median 1.46 nL; range 0.14–29.79). These
globules also appeared to lack hygroscopic properties
causing them to quickly desiccate after production
and lose their adhesive properties. Rate of desiccation
was dependent on size with larger globules taking
longer to dry. Most globules completely desiccated in
less than five minutes. We also show that this defen-
sive silk forcefully contracts after production. When
silk was suspended between thin wires the distance
between wires was reduced by a median 2.88% (range
0.44–6.32). These properties may equip the defensive
silk of this species to immobilize arthropod predators
and allow the spider to escape.
Keywords: defensive silk, Latrodectus, viscid globule
20th International Congress of Arachnology