Abdominal color variation in two syrphine flies and its possible role in mimicry

Two syrphine flies (Diptera: Syrphidae) were studied to measure the possible difference in the abdominal color pattern variation of sternites 2-5. Toxomerus marginatus, a non-mimetic syrphine, shows much more variation in its abdominal color pattern than Ch,ysotoxum derivatum, a high fidelity syrphine mimic of vespid wasps. Chrysotoxum derimtum also showed stability of its abdominal color pattern with little heterogeneity of abdominal color pattern types. It is assumed that organisms under strong selection pressure for a phenotypic character will show a narrow range of phenotypes for that character in a population. This study demonstrates that the homogeneity of the mimetic abdominal color pattern of Chrysotoxum derivatum is probably due to discriminatory visual predation.