Utilization of aphid honeydew and floral nectar by Pseudacteon tricuspis (Diptera: Phoridae), a parasitoid of imported fire ants, Solenopis spp. (Hymenoptera: Formicidae)

Abstract

Abstract We examined the effects of cotton aphid honeydew and buckwheat floral nectar on the lifespan and body carbohydrate nutrient levels of the phorid fly, Pseudacteon tricuspis (Diptera: Phoridae). Compared to flies provided with water only, cotton aphid honeydew modestly but significantly increased longevity of female and male P. tricuspis by about 1 day, with significant increases in the body levels of fructose, total sugars, and glycogen. Age had a positive effect on the levels of total sugars and glycogen in honeydew-fed flies. However, sex and mating had no significant effect on longevity and body nutrient levels. Body size (as measured by wing length) was positively correlated with glycogen levels in males, with larger males accumulating more glycogen from honeydew than smaller males. P. tricuspis flies were observed foraging on buckwheat flowers. However, no significant effects of buckwheat nectar on phorid fly longevity and body nutrient levels were detected. These results may suggest that buckwheat florets are morphologically incompatible with the mouthparts of phorid flies, or the possibility of innate behavioral characteristics of phorid flies that limit nectivory. Alternatively, buckwheat nectar may be quantitatively or qualitatively inferior to cotton aphid honeydew or may contain compounds that are mildly repellent to P. tricuspis. Future studies will investigate the mechanisms behind the observed reduced suitability of buckwheat nectar as a food source for P. tricuspis. Conservation of naturally occurring sugar sources in the field, including exposed sugar sources such as honeydew, may promote P. tricuspis lifespan and possibly, its impact as a biological control agent against imported fire ants, Solenopsis spp. (Hymenoptera: Formicidae).