Preliminary identification of a putative lycosid kairomone
The wolf spider Pardosa milvina shows effective antipredator responses (reduced activity) in the presence of silk and excreta from a larger co-occurring wolf spider predator, Hogna helluo. We examined the proximate cues involved in eliciting antipredator behavior in P. milvina. First, using automated video-tracking software (Ethovision), we measured P. milvina activity level on four substrates: 1) silk only, 2) excreta only, 3) silk and excreta, and 4) a blank control to test for possible additive or synergistic effects of these two components. Second, we dissolved silk and excreta in methanol and precipitated the solution on to sheets of filter paper. Pardosa response was then measured on these sheets and compared to intact silk and excreta to measure possible interactions between tactile and chemical cues involved in P. milvina response. We found a significant difference in Pardosa response to the four treatments. Pardosa showed a significant reduction in activity in the presence of silk and excreta or silk alone compared to excreta alone or the blank control for five out of six measured behaviors. However, excreta alone did produce a significant reduction in activity compared to the control for one measure of activity. We conclude that Hogna silk is the primary cue used by Pardosa to detect this predator. Whether silk-induced antipredator behavior is primarily detected using chemical information or tactile information has yet to be determined. More results later.