Sex Specific Selection by a Parasitoid on Body Size in its Newly Recognized Host

Abstract

We identified the tree cricket Oecanthus nigricornis (Orthoptera; Gryllidae) as a host species used by the parasitoid fly Stylogaster neglecta (Diptera: Conopidae). We describe several life history aspects of the parasitoid-host interaction including: the identification of a host, timing of parasitism, estimates of incubation time, preferred life stage of host, and variance in rates of parasitism across space. We also examined size biases in parasitism amongst crickets to determine if there is selection on body size. We found that there was a significant effect of sex, whereby males are more likely to be parasitized than females, and an interaction between the square of body size (non-linear selection) and sex. Upon examining the effect of body size individual for each sex, we found that in males, there was positive linear selection on body size and positive non-linear selection on body size, indicating higher parasitism in smaller and intermediate sized crickets.