Print PageSpiders are classically used as an example of sexual size dimorphism among invertebrates. Theories postulated to explain the evolution of such gender differentiation include sexual selection for increased female size, differentiation in reproductive roles, and intersexual niche divergence to reduce competition in resource acquisition. Spiders of the genus Lycosidae are relatively unique among the Araneomorphae in that the degree of sexual size dimorphism is greatly reduced, however it is still present. Genders may also exhibit behavioral foraging contrasts. Male wolf spiders tend to wander more while females are more sedentary. Such morphological and behavioral dichotomies among sexes may results in differential predation success. The objective of this study was to identify the degree of behavioral and morphological variation in Hogna helluo (a cursorial Lycosid with an extensive geographical range). Spiders were captured by headlighting in local parks after dusk. Males, gravid females, and non-gravid females were introduced into experimental chambers with several levels of prey density to identify differences in behavioral foraging strategies. Morphological variation was examined among the three experimental groups using digital microscopy.
Results/Conclusions
Preliminary data analysis indicates that morphological differentiation exists between males and females, but not between gravid and non-gravid females. Leg segment length also showed no differences among the experimental groups. At increasing densities of prey, males did not differ from females in intercapture interval, however gravid and non-gravid females did. Experimental groups did not differ in the number of prey consumed at similar prey densities. Results indicate that gravid females may be capturing prey at a faster rate due to the physiological consequences of offspring production. Behavioral homogeneity may suggest that intersexual niche divergence is not a major contributing factor to the evolution of sexual size dimorphism.
