Interspecific Mouthpart Length Variation and Floral Visitation in the Parasitic Wasp Genus Agathirsia (Braconidae: Agathidinae)

Carbohydrate energy sources are known to be important for many adult parasitic wasps. Floral visitation is commonly observed, and in many groups specialized mouthpart morphology is associated with deep nectar extraction. In parasitic wasps, there are few data examining the relationship between host plant use and the length of the mouthparts. In an effort to associate mouthpart length to nectar source, pollen was identified from museum specimens of selected species of Agathirsia (Hymenoptera Braconidae). Despite drastic differences in glossa length, the pollen of several species of Asteraceae were commonly found on specimens of various species. We infer that increased feeding efficiency, as opposed to nectar access, is the adaptive value of elongate glossae in Agathirsia. Species with short mouthparts, however, exhibited a difference from both the medium and long mouthpart categories in pollen similarity. This suggests that members of Agathirsia with elongated mouthparts are more apt to visit certain flowers compared with short-tongued species. Males and females exhibited considerable overlap of their common nectar sources and displayed similar pollen richness. Pollen richness was higher in species in the medium length category compared with the short category, but these results are confounded by the fact that the medium-length specimens were on average larger bodied.