Quantitative genetics of immune function and body size in the house cricket, Acheta domesticus

Female house crickets are attracted to male calling song containing a relat ively high number of syllables per 'chirp', which tends to be produced by l arge mates. in a previous study, we showed that this song characteristic is also positively and independently correlated with haemocyte load, an impor tant determinant of the ability to produce an encapsulation response in ins ects. Females will therefore tend to select males with high encapsulation a bility (and large body size) as mates. The present study demonstrates that variation in haemocyte load and body size, together with a second parameter of immune function (the ability to encapsulate a synthetic substrate), is heritable in the same population. Moreover, all three traits are shown to b e positively genetically correlated. In favouring males that produce callin g song with the preferred characteristics, females should therefore also te nd to produce larger offspring with a greater ability to produce an encapsu lation response.