Vibratory Communication in the Black Widow Spider, Latrodectus hesperus (Araneae: Theridiidae)

Several studies have described vibration producing behaviours across many web-building spiders, and vibratory communication is thought to play an integral role during male-female interactions. Despite the presumed ubiquity of vibratory communication in this group of spiders, very little is known about the characteristics and functions of the signals involved, how signals are produced and transmitted through webs, or how vibrations are perceived. In this thesis, I used the western black widow spider, Latrodectus hesperus, as my focal organism, to investigate the details of vibratory communication from sender to the receiver. My results show that male L. hesperus courtship vibration signals comprise three distinct components (abdominal tremulation, bounce and web plucks), each produced using different signal production mechanism. Larger males produced bounce and web pluck signals with high power, which suggests that these signals may carry information about male traits. I found that during the early phase of courtship, males produced these different signal components haphazardly, with little temporal organization among the individual components (unstructured signaling). However, during the later phase of courtship, as males approach females, males intermittently organized signal components into a stereotyped temporal sequence (structured signaling). I tested the importance of these composite multicomponent signals, and found that males that displayed these structured signals more often were more likely to successfully copulate and copulate sooner. Vibrations arriving at the females are transmitted through the legs. My results show that the more distal joints of the legs (i.e. tarsus-metatarsus joint) move more to higher frequencies, and more proximal joints are tuned to lower frequencies. This suggests that female leg-joints play an important role in segregating vibration frequencies, and this may have important implications for prey/mate discrimination, as well as vibration source localization. These results show that L. hesperus males employ multiple signal components during courtship, and provide novel insights into emergent signal complexities in a web-building spider, previously thought to be ‘simple’ signalers. Additionally, the spider body mechanics can play a key role in influence vibration perception.

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