Biology of three Harpalus species (Coleoptera: Carabidae)—Flight muscle polymorphism, feeding habits and reproductive phenology

Abstract

We examined the ecology of Harpalus griseus, H. eous and H. tridens captured with aerial traps (malaise and flight interception) as the representatives of flying carabids. Using both aerial and pitfall traps, we examined their seasonal activity and hind wing conditions. We also investigated by dissection the phenology of flight muscles, reproductive organs, and gut contents. All three species emerged early summer and matured in mid-September. Their eggs were large but few. Harpalus tridens was caught less often in aerial but more often in pitfall than the other two species, indicating H. tridens has lower flight ability than the other two species. Although all three species were macropterous, the relative lengths of hind wing to both body and elytron were highest in H. griseus followed by H. eous and H. tridens suggesting the relative lengths can be a useful parameter of flight ability. Harpalus tridens also showed a lower rate of individuals with flight muscles than the other two, suggesting some individuals of H. tridens lack muscles during the entire adult stage. We revealed all three species exhibited flight muscle polymorphism, and lost muscles before breeding probably owing to histolysis. Gut dissection revealed that they mostly fed on seeds and partly on arthropods. Animal fragments were found more often in the guts of H. tridens than the other two. Probably, flying is important to find seeds of plants, establishing certain relationship between the diet and flying ability. Our study clearly implicates peculiar evolutionary ecological pathways of carabids.