Colour patterns of syrphidae: IV. Mimicry and variation in natural populations of eristalis tenax

Abstract

The dronefly, Eristalis tenax L., and the honeybee, Apis mellifera L., are similar in their general form, flight and coloration. Experiments with captive birds showed that E. tenax are very palatable, although they may be avoided if given after honeybees. Thus the mimicry is of the Batesian variety.Both model and mimic vary in colour pattern. Although the phenotypic variation is continuous, in both species it is also bimodal owing to genetic polymorphisms which are modified by other factors. In north-west England the overall percentage of “light” patterns was roughly 50 per cent, both in the model and in the mimic. Pattern frequencies in E. tenax were fairly consistent between samples, as expected for a highly mobile species, but honeybees showed local fluctuations. In spring, E. tenax was less variable, and much less numerous, than it was in autumn.Although similar in colour, the markings on the abdomens of the two species differ in shape. Possible reasons why Eristalis tenax has not evolved a more exact resemblance to Apis mellifera are that the modified patterns derive some added protection from a partial mimicry of wasps, and that they are more effective in temperature regulation. © 1982 The Genetical Society of Great Britain.