The effect of diet and parasite load on female phonotaxis in the Texas field cricket, Gryllus integer

Female crickets respond selectively to variations in species-specific male calling \nsongs. This selectivity has been shown to be age-dependent; older females are less \nchoosy. However, female quality should also affect female selectivity. The effect of \nfemale quality on mate choice was examined in Gryllus integer by comparing the \nphonotactic responses of females on different diets and with different parasite loads to \nvarious synthetic models of conspecific calling song. Test females were virgin, 11-14 \ndays old, and had been maintained on one of five diets varying in protein and fat \ncontent. Phonotaxis was quantified using a non-compensating Kugel treadmill which \ngenerates vector scores incorporating the speed and direction of movement of each \nfemale. Test females were presented with four calling song models which differed in \npulse rate, but were still within the natural range of the species for the experimental \ntemperature. After testing, females were dissected and the number of gregarine \nparasites within the digestive tract counted. \nThere were no significant effects of either diet or parasitism on female \nmotivation to mate although the combined effects of these variables seem to have an \neffect with no apparent trend. Control females did not discriminate among song types, \nbut there was a trend of female preferences for lower pulse rates which are closest to \nthe mean pulse rate for the species. Heavily parasitized females did not discriminate \namong pulse rates altho~gh there was a similar trend of high vector scores for low \npulse rates. Diet, however, affected selectivity with poorly-fed females showing \nsignificantly high vector scores for pulse rates near the species mean. Such findings \nraise interesting questions about energy allocation and costs and risks of phonotaxis and \nmate choice in acoustic Orthoptera. These results are discussed in terms of sexual \nselection and female mate choice.