Melanism in Adalia bipunctata L. (Col., Coccinellidae) and its Relationship to Atmospheric Pollution

Sperm competition and melanic polymorphism in the 2-spot ladybird, Adalia bipunctata (Coleoptera, Coccinellidae)

“…An hypothesis about the way in which selection influences the colour polymorphism involves thermal melanism, in which the melanic morph has an advantage relative to the lypica morph under circumstances of limited sunshine levels (Lusis, 1961;Muggleton et at., 1975;Brakefield, 1984b;Brakefield & Willmer, 1985;Brakefield & Lees, 1987). An essential feature of this hypothesis is the presence of food (aphids) for the ladybirds.…”

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

“…Indeed, in Great Britain there is a significant negative correlation between melanic frequency and mean winter temperature (r = 0508, n = 32) although this may be related to the correlation between mean winter temperature and annual sunshine hours at the same sites (r = 0662, n = 32). In Great Britain sunshine levels appear to be one of the major factors determining morph frequency (Muggleton et al, 1975).…”

“…(ii) Selection during the summer Muggleton et al (1975) suggested that the greater heat absorption and activity of the melanie morphs would put them at a disadvantage during the summer months as a result of overheating and desiccation and Hodek (1973) points out that for many polymorphic ladybirds there is a tendency for increases in melanic frequency to be associated with increasing humidity. The relationship between high melanie frequencies in A. bipunctata and high humidity has been stressed by Lusis (1961) and, more recently, by Bengston and Hagen (1977).…”

“…Thus it is probable that at least in areas of high melanic frequency a lack of migration is reducing the spread of the melanic morphs. This, in turn, suggests that the existence of low melanic frequencies in isolated industrial towns cannot be explained in terms of migration and that an explanation for it must be sought elsewhere (see Muggleton et al, 1975). In contrast to the other melanic polymorphisms in invertebrates, the possibility that selective predation is a factor maintaining the polymorphism in A. bipunctata has been ignored on the assumption that ladybirds are aposematic and avoided by vertebrate predators.…”

“…Intermediates are rare but when they do occur can be classified by reference to the forms depicted by Lusis (1932). The nature of the factors maintaining this polymorphism in Great Britain has been the subject of recent discussion (Creed, 197la, 1975;Muggleton, Lonsdale and Benham, 1975) and for the most part this discussion has concentrated on those factors that advantage the melanic morphs. Yet, in spite of the fact melanics are dominant and have been present since at least 1696 (Hammond, 1975), populations with high frequencies of melanics are uncommon and throughout most of the range of this circumboreal species high frequencies of typicals are found.…”