Comma

Photo by Trevor Baker

Comma Polygonia c-album (Linnaeus 1758 )

Family: Nymphalidae, subgroup Nymphalinae (the “Nymphalids” or “Vanessids”)

Description

by Dave Hatton

by Dave Hatton

by Michelle Smart

The Comma is very similar in looks to a Small Tortoiseshell, but with scalloped wings and a more even orange brown coloration lacking blue spots. It can also be confused with Wall Brown and some Fritillaries. The Comma’s undersides vary from dark brown to near black, with a marbling of ochre and bronze green, and the usually distinctive white comma mark on the hindwing.

Males and females are very similar, but females tend to be larger with less ragged edges and a more even dark coloration on the underside. Up to 40% of the first brood have brighter, more golden orange upperparts and much paler underparts with less strongly scalloped wings. These are known as the hutchinsoni form, after Emma Hutchinson (b 1820/d 1906) who was first to breed them and discover that only this colour form produced the second brood.

Habitat

The species’ preferred habitat is sunny open woodlands, woodland rides, edges or clearings, or country lanes. The most widely used foodplant is Common nettle (Urtica dioica). Other species used include Hop (Humulus lupulus), elms (Ulmus spp.), currants (Ribes spp.) and Willows (Salix spp.).

Circumstantial evidence suggests Wych Elm may be a main (if not the main) foodplant in Yorkshire. Similar observations have been made in Northumberland and Durham where 50% of observations have been specifically on wych elm (pers comm. Ian Waller).

Late summer adults range widely through gardens or orchards in search of nectar plants and rotting fruit on which to feed up prior to hibernation. They will also visit animal droppings, including half-dried dog faeces, probing for salts (pers obs.). Hibernated butterflies may awake on warm, winter days in Jan/Feb, and nectar on ‘Pussy’ Willow (Salix capraea) and other species of catkins, but the majority are more likely to emerge from early March onward. As most Commas hibernate and breed in woodland areas, they are not as evident in gardens in spring as they are in autumn. Males establish territories and seek out females. Mating appears to take place unseen, high up in trees, perhaps at night.

Distribution

The Comma was once widespread over most of England and Wales, and parts of southern Scotland, before a major decline in the 1800s left it confined to the Welsh border counties. This is likely due to a reduction in hop farming, which was its key larval foodplant at that time. Since the 1960s the butterfly has made a dramatic comeback, thought to be due at least partly to the switch to the widespread common nettle as one of its key larval foodplants.

The Comma is now widely distributed throughout Southern England, and its range is expanding northwards throughout Britain, helped at least in part by climate change. This trend is mirrored in its Yorkshire distribution, with sightings across all parts of the county and particular strongholds in the south and centre of the county. Populations in the county have waxed and waned considerably over the last 200 years with virtual extinctions following clusters of cool or cold years.

Many sources suggest it does not appear to migrate across areas of sea. But its sightings on the Isle of Man and in Ireland, as well as a sighting 3.5km off the Cornish coast, and an occasional presence on the Isles of Scilly (Wacher et al 2003), suggest that past sea crossings may have been overlooked.

Life Cycle

The Comma has a flexible life cycle, which allows it to capitalize on favourable weather conditions. The butterfly can be seen at any time of the year, occasionally awakening on warm winter days. The butterfly emerges from hibernation in March, giving rise to the next generation which appears at the end of June and start of July.

The first Yorkshire sighting in 2019 was 12 January in Langtoft, Driffield.

The last Yorkshire sighting in 2019 was 16 November at Norwood Edge, Otley.

Females lay 10 to 25 eggs on each suitable day, which hatch after 2 to 3 weeks, becoming drab, brown larvae with a white splodge helping to disguise them as bird droppings. The 1st brood larval period lasts around 4 to 7 weeks depending on which colour form is involved. Pupae resemble withered leaves and hang from a pad of silk under a leaf or branch of the foodplant.

First brood adults come in two forms – the normal dull brown form with dark undersides go on to hibernate (the darker colouration offering better camouflage during winter). The hutchinsonii form, which have lighter undersides and brighter uppersides better adapted to dodging predators in bright summer sun, go on to produce a second brood in late summer.

The proportion of colour types seems to be determined by daylight length during the larval stage (although Emmet & Heath (1989) suggest succulence of foodplant also plays a part). First brood larvae, which develop before the solstice, are likely to be hutchinsoni. Those developing as day length shortens will grow more slowly and emerge later as the normal darker form whose prime purpose is to hibernate successfully in readiness for mating the following spring.

The proportion of hutchinsoni will vary from year to year according to weather conditions and latitude. An early emergence from hibernation is likely to increase chances of higher numbers of hutchinsoni. As one moves north the occurrence of a 2nd brood becomes more sporadic, and limited to exceptionally good summers.

Where two broods occur, both may be on the wing at the same time in autumn, giving rise to a larger number of butterflies ranging widely in search of nectar and fruit to build up reserves in preparation for hibernation. Hibernation often takes place on tree trunks and branches, and occasionally in caves, hollows and open buildings. The butterfly looks like a dead leaf with the comma mark appearing to be a crack in the leaf, whilst the white legs can merge into the mosaic of lichens found on the bark.

Status

The species is not under threat.

Aberrations

Although major variation is rare, over 30 aberrations have been described. Ground colour can vary considerably from almost white (ab albus Frohawk) or pale straw yellow (ab dilutus Frohawk), to examples where the dark markings join together (ab suffusa Tutt), or the hindwing is almost black (ab reichenstettenis Fettig). The amount of ochre and metallic green on the underside may vary as can the ‘comma’ mark in size or shape. More rarely it may even be missing (ab extincta Rebel).

E Ingram 18/11/20