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