A department of the College of Agriculture and Life Sciences at Cornell University

Dr. Linda S. Rayor Department of Entomology 4130 Comstock Hall Cornell University Ithaca, NY 14853

Senior Research Associate

Web Sites of Interest:

http://www.entomology.cornell.edu/Faculty_Staff/Rayor

http://cybertower.cornell.edu   'A Romance With Spiders' by Linda Rayor

http://www.entomology.cornell.edu/NaturalistOutreach   Naturalist Outreach in Biology

http://www.entomology.cornell.edu/SpiderOutreach/   'Spider Outreach Program: Eight-legged Ambassadors for Science Education' and Resources for Teachers

http://www.arachnology.org   See 'Arachnology Pages' for general spider inquiries

Research Interests:

I am an arthropod behavioral ecologist with special interest in the interactions between predatory and social behavior. My research examines the costs and benefits of group living in social, but readily cannibalistic, predators. I am particularly interested in the trade-offs that obligate predators make to live in social groups. For example, group members may benefit by sharing prey or evade other predators more effectively in the group, but remaining in the group may also reduce their own reproduction. Understanding the factors that influence the evolution of social behavior and how social groups function are central issues in behavioral ecology today.

My current research interests are in two areas: (1) Conflict and cooperation in an extremely atypical social huntsman spider, Delena cancerides [Araneae: Sparassidae], and (2) Patterns of social communication and exploration in social whip spiders (Arachnida: Order Amblypygi). I have a (currently inactive) interest in the behavioral and fitness consequences of predation by generalist paper wasps on chemically defended caterpillars in tritrophic interactions.

Conflict and Cooperation in Social Huntsmen Spiders:

The primary research in my laboratory is on the social behavior, mother-offspring dynamics, colony formation, and sexual conflict in the endemic Australian huntsman spider, Delena cancerides (Sparassidae). Delena were the spider stars of the 'Arachnophobia'!

Sociality in spiders is extremely rare. Less than 1% or ~40 spider species are social. Delena canerides is considered to be the most unusual of the known social spiders with important characteristics that differ from those of all other social spiders. Unlike all other social spiders, they do not live in webs, are extremely aggressive to non-colony mates, have a 1:1 sex ratio, and are highly outbred with unusual chromosomal races (Rowell & Aviles 1995). Delena simply do not fit any cur­rent understanding of spider sociality. Delena are large non-web building spiders that live under the bark of dead trees in year-round colonies of up to 300 individuals. The narrow bark-covered retreats are relatively rare and can readily be defended from intruders, unlike the relatively open web-based colonies of other social spider species. The social demographics of Delena vary along a continuum from a single breeding female with multiple clutches of offspring to the substantially more complex dynamics of multiple adult social groups. Although they lack communal webs that facilitate cooperative prey capture and communication, Delena share prey and interact frequently with a diverse behavioral repertoire. Delena exhibit important components of conflict and cooperation more typical of eusocial insects than social spiders, including aggression toward non colony-mates and competition between reproductive females. Even courtship and mating is unusual in these spiders, as these huntsmen spiders mate for hours, with many partners, and males may simultaneously attempt to copulate with females! Because of the confluence of unusual behavioral and genetic traits, Delena cancerides are a wonderful system to test theories of social evolution and group living.

Projects on Delena cancerides in my laboratory include:

• A comparison of courtship, mother-offspring interactions, prey sharing, and growth rates in Delena with those seen in solitary huntsmen spider species.

• Studying the social dynamics in colonies with different social demographics.

• Examining the role of prey availability and retreat size on social dynamics.

• Consequences of sociality on courtship and mating patterns in Delena

• Experiments and simulation models to determine which factors affect individuals' decisions to remain with the social group or depart from the natal colony.

• A determination of genetic relationships within Delena colonies, in collaboration with Dr. David Rowell, Australian National University.

• Investigate factors involved in kin recognition and aggression between non-colony mates.

(See Cornell Cybertower http://cybertower.cornell.edu – A Romance with Spiders by Linda Rayor for more information and videos of the huntsmen spiders. Go to 'Social Spiders and Community Outreach')

Amblypygid Social Behavior:

A close relative of spiders are the whip spiders or amblypygids (Arachnida: Amblypygi). Like spiders and most other arachnids, the amblypygids have two body parts, eight legs, and palps. But the dorso-ventrally flattened amblypygids have enlarged palps that capture prey and the thin elongate first leg (or 'whip') is extremely flexible. Amblypygids lives are centered on the sensory information they acquire through their antenniform whips. Amblypygids have been considered to be solitary and highly aggressive to conspecifics, not social. However, in captivity we have discovered that amblypygids from two families are subsocial, with complex communicative and social interactions that last until sexual maturity at 1-year of age.

Research on amblypygids in my laboratory has focused on amblypygid social dynamics, kin recognition, and ontogenetic changes in behavior. We have found that in Damon diadema (Family Phrynichidae) there is prolonged association and tolerance between mothers and their offspring, active aggregation, frequent amicable tactile interactions, and kin recognition. In captive groups, D. diadema demonstrate all of the traits characteristic of social spiders with the exception of cooperative prey capture. These traits include: (1) Prolonged association with conspecfics, (2) a high level of tolerance (3) a strong tendency to aggregate, (4) overlapping generations of kin, and (5) communicative behavior. Immature amblypygids and their mothers form large interactive groups that are in constant tactile (whip) contact with one another. Young D. diadema remain closely associated and highly interactive until they reach sexual maturity at approximately 12 - 15 months, at which time they avoid interaction with one another except when coming together for courtship. Patterns of grouping and proximity change gradually as the amblypygids mature. We have developed a detailed behavioral ethogram for Damon diadema to quantify the frequency of behavioral interactions. Agonistic interactions among siblings are mild and infrequent prior to sexual maturity. Young siblings (4 to 6 months) interact constantly and are significantly more amicable than interactions among subadult siblings (10 to 11 months) or within mixed groups of unrelated animals. Agonistic behavior is significantly higher among unfamiliar individuals than among sibling groups. When experimentally disturbed or moved into an unfamiliar environment, young amblypygids immediately aggregate with one another and move closer to their mother. Exploring amblypygid communication and social dynamics is the current focus of this system in my laboratory.

(To see videos and more images of the amblypygids engaged in social interactions go to Cornell Cybertower [put in link: http://cybertower.cornell.edu] – 'A Romance with Spiders' by Linda Rayor. The amblypygid videos are in the section 'Social Spiders and Community Outreach'.)