Selection against the melanic morphs of Adalia bipunctata (two-spot ladybird): A review and some new data

Abstract

SUMMARYWork on the nature of the factors selecting against the melanie morphs of Adalia bipunetata is reviewed, New data are presented showing that there is normally one generation per year in Great Britain and that the cyclical changes in morph frequency observed in Berlin may not occur in Great Britain.The roles of migration and selective predation in limiting the spread of the melanie morphs are discussed and evidence is presented to show that predation by birds on ladybirds occurs more frequently than previously supposed.In conclusion it is proposed that the melanie frequency of a population is the result of the interaction of a number of factors whose importance varies from locality to locality.

Evidence for preferential mating in Adalia bipunctata

“…The frequency of melanics in the Keele population is 31.66 per cent. The results presented are therefore consistent with the general finding of Muggleton (1978) that there is an excess of melanics amongst mating pairs compared with their frequency in the population as a whole when melanics comprise less than 40 per cent of the population. However, this does not mean that we would expect to find preferences for quadrimaculata males in all populations where quadrimaculata males constitute less than 40 per cent of the population.…”

“…It may be as little as 21 days in the laboratory, although five to eight weeks is probably usual in the wild in Britain. Muggleton (1978) suggests that in England A. bipunctata is univoltme. He noted that in southern and eastern England there was apparently only one generation in 1976, no mating pairs being observed after the end of June.…”

Differences between the 7‐spot and 2‐spot ladybird beetles (Coccinellidae) in their toxic effects on a bird predator

“…Muggleton, 1978). Brakefield (1985) suggests that different types of mimicry may be shown by different species.…”

“…Again, records of bird prédation on A.bipunctata are somewhat equivocal, but we have recorded them being fed to the nestlings of blue tits in suburban areas of Cardiff (R. J. Cowie and S. A. Hinsley, unpublished data). They are also taken by aerial feeders such as swifts Apus apus and house martins Delichon urbica (Owen, 1955;Muggleton. 1978).…”

“…Other factors which are known to influence the polymorphism, such as thermal melanism and sexual selection (see Muggleton, 1978;Brakefield, 1987), are also unable to account for the colour patterns per se of the different forms.…”