Comma
Polygonia c-album, the comma, is a food generalist (polyphagous) butterfly species belonging to the family Nymphalidae. The angular notches on the edges of the forewings are characteristic of the genus Polygonia, which is why species in the genus are commonly referred to as anglewing butterflies. Comma butterflies can be identified by their prominent orange and dark brown/black dorsal wings.
Both the larval and adult stages exhibit protective camouflage, mimicking bird droppings and fallen leaves respectively, which reduces predation. The pupae are also cryptic, resembling shriveled leaves. During the later stage of development, the larvae also develop strong spines along their backs. The species is commonly found in Europe, North Africa, and Asia, and contains several subspecies. Although the species is not migratory, the butterflies are strong fliers, resulting in an open population structure with high gene flow and increased genetic variation.
The outer margins of the wings are strongly and irregularly dentate, excavated and angulated.The upper side of the wings has a bright orange ground colour, decorated with brown marks and light spots on the edge. The reverse is marbled with brown. Folded, the butterfly looks like a dead leaf. The hindwings have on the reverse side a white spot usually in the shape of C.
The sexual dimorphism is slight and concerns the intensity of the coloration, the silhouette and the size, the male having a wingspan of 22 to 24 mm. and the female of 25 to 26 mm. The seasonal dimorphism is more marked: the first generation ( hutchinsoni form, named for Emma Hutchinson, May-June) has the upperside fawn orange and the underside brown-gold and the hindwing bears distally a broad dark red-brown area in which is situated a row of light brown hastate spots, the underside is dark, being either unicolorous or prominently marmorated., while the second generation (form c-album (July, in autumn and spring after overwintering) has a more reddish upper and dark brown underside (ground-colour is less bright). In the summer-form the wings are less dentate, and the hindwing has a narrow dark submarginal band, near which stands a row of light lunules proximally bordered by a band of brown arcs; the underside is of a paler colour, being less distinctly — sometimes, however, very prominently — marmorated and shaded.
The comma inhabits areas including Europe, North Africa, and Asia. It is primarily a woodland butterfly, living in low-density forests with sunshine and moist soil. Specifically, the species is commonly found in the woodland, country lanes, and garden areas of Norway, Sweden, and Great Britain. As a food generalist, or polyphagous species, comma butterflies can feed upon a variety of host plants, leading to widespread ranges across continents. In response to climate change, they are also undergoing range expansion.
Comma butterflies have a polyandrous mating system where females mate with multiple males to receive the necessary amount of sperm to fertilize their eggs. The polyandrous female distributes her matings equally over her lifetime, so males' mating success increases proportionally to their lifespan. The mating success of both sexes is correlated to the duration of an individual's life, so no difference in mortality rates is observed between males and females.
In the 19th century, the British population of the comma crashed, possibly as a result of reduced hop (H. lupulus) farming. From about 1930 the population recovered, and the comma is now one of the more familiar butterflies in Southern England. It is also found in Scotland and in North Wales. Since the 1970s in Britain, specialist butterflies have decreased in population as their preferred habitat and host plants area becomes smaller. On the other hand, generalist species such as P. c-album have started to expand their range. In particular, comma butterflies have expanded along the northern edge of their range.
