David L. Clark, Ph.D.
Directed Student Presentations and Achievements
Ms. Meghan Rector , Environmental Influences of Courtship in the Wolf Spider Schizocosa ocreata
Abstract: During the breeding season, male wolf spiders (Schizocosa ocreata) expend considerable energy searching for females and run a high risk of predation by exposing themselves to potential predators. In the leaf litter there is considerable variation in temperature on leaf surfaces and in ambient light characteristics. This study was divided into two parts; 1) Survey variation in leaf litter temperature and of courting males; and 2) Examine reflectance patterns of male spider body parts and compare these to the spectra of leaf litter. There was no significant difference between the temperatures of courting males (22.47 oC) and non-courting males (22.56 oC) (students t-test, t=0.139; DF=114; P>0.05). Interestingly, the mean temperature of male spiders was between the means of leaves found in the sun and leaves found in the shade at 22.52 oC. Spectral analysis of spider body parts showed that some parts of the spider appear exceptionally dark (e.g., the lateral view of leg tufts), while other aspects (dorsal median stripe) appear more closely matched to the spectra of leaf litter. This revealed that the more negative radiance of tufts makes for greater contrast with the lighter background of leaf litter, but that dorsal coloration contrasted less with the litter background. These results suggest that wolf spiders maximize contrast and exposure when viewed from the side (by female spiders), while minimizing potential for detection from above (predators) by cryptic coloration.