Spider prey selection and avoidance of toxins.

Abstract

Animals practice a wide variety of foraging techniques, all designed to obtain the most energy out of foraging in the least amount of time. Spiders are sit and wait predators that construct webs that facilitate prey capture. Spiders practice active prey selection to find an optimal compromise between energy-rich prey and prey with poor nutritional value or toxicity. I set out to determine if spiders have a mechanism to avoid toxic insects by placing toxic (milkweed bugs, willow flea weevils, stink bugs) and non-toxic (flies) insects into spiders webs and observing whether they were consumed. I predicted that spiders would feed on toxic insects less frequently than non-toxic insects to avoid the negative nutritional value of the toxins. I also proposed that there would be different consumption rates at differenct web heights and web diameters. Using a X2 test I found no difference among insect species as to which were consumed or not consumed (X2=1.994, df=3, P=0.574). There was a slight trend that flies were preferred since 40% of flies were consumed. I performed an analysis of variance, which showed an interaction between prety type and web type (F=2.183, P=0.067). This interaction indicates that certain prey are preferred or avoided in certain web types. There was no significant relationship between web height or web diameter and the consumption of any species (Height: F=1.43, P=0.259 - Diameter F=1.538, df=47, P=0.239). My data does not support my original hypothesis that spiders would feed on toxic insects less frequently than non-toxic insects. This was most likely due to the lack of repeated feeding of toxic insects to individual spiders allowing them to develop a tolerance or an acquired aversion towards the toxic prey.