The upperside  can look like a very tatty worn  Small Tortoiseshell, but with scalloped wings and a more even orange brown coloration and  lacks the blue spots its fairly easy to identify.  It can be confused with Silver-washed Fritillary which  flies in the same habitat.  The Comma’s undersides closely resembles a dried up leaf varying from dark brown to near black, with a marbling of ochre and bronze green, and the usually distinctive white C mark on the hindwing.  When seen, wings closed, on a dried bracken leaf everything makes sense as the mimicry with the scalloped edges and subtle marbling and colouration is perfection. Its no surprise that it is often seen in number where bracken abounds  in woodlands clearings.

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 half 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. In July females can sometimes be seen searching and closely inspecting shoot tips of Elm branches with flight resembling an oversized White-letter hairstreak. 

Males establish territories aggressively investigating any species that come by,  sometimes causing a neighbouring male to spiral upwards in combat. The triuphant resident returns to his perch  Mating appears to take place unseen, high up in trees, perhaps at night. Many sources suggest it does not appear to migrate across areas of sea.  But  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 sea crossings may be quite common.

The species’ preferred habitat is sunny open woodlands, woodland rides, edges or clearings, or country lanes. The most widely used foodplant is Common nettle usually in partial shade. Other species used include Hops and Wych elms in Yorkshire but occasionally on Willow and Hazel. Circumstantial evidence suggests Wych Elm may be a  prefered foodplant where it occurs.  Observations have been made in Northumberland and Durham where 50% of records have been specifically on Wych Elm (pers comm. Ian Waller).  Woods with more Elms tend to have larger populations of Comma.  Studies has shown that Elms are  the prefered  foodplant the further north you go but as temperatures rise survival rates on nettle are much  better.   

Its distribution  has waxed and waned over the years corresponding to cooling/warming spells in our ever changing climate. It was well known in Yorkshire untill 1816 when biggest volcanic eruption ever by Tambura ment there was no summer  that year and almost all butterfly populations crashed.  Comma recovered strongly with a warm period in 1830's  up till the 1870's while spreading well up into Scotland  during this time. The UK population then crashed  after the Krakatoe  eruption and the following cold period 1879-1895 except  for Welsh border counties Gloucestershire and Hereford where it remained common in the counties hopyards. Hops were the prefered foodplant at this time,  however in Europe nettles are prefered.  It returned to Yorkshire in the warm period of the 1930 and 40's, and its foodplant changed to nettle suggesting that these might be europeans  taking advantage of the warming climate plus we know that nettles are favoured.  In the  later 50's and 60's it declined once again, as it became cooler reaching a modern day minimum in the mid 60's and was almost absent apart from early Autumn wanderers until about 1982 when the current expansion recommenced and continues at an ever increasing rate and in 2023  greatly outnumbered Small Tortoiseshell and even Peacock in the Vale of York to reach and all time high .  The contrast with Small Tortoiseshell is stark as that species  became almost absent in much of the Humberhead and south half of the Vale of York and  increasingly confined to cooler areas  above 100m during the current  run of hot summers. The Comma seems well adapted to deal with heat and this likely due to its flexability in producing a summer brood  which has become very difficult for Small Tortoiseshell which has been forced to hibernate in June.

World Status  

In the last decade it has crossed the channel and established in southern Ireland as well as now spreading up well into scotland reaching the great glen. Much of France and eastwards across Central Europe to south Finland, extremely local in north Spain. North Africa, and Asia. It is primarily a woodland butterfly, living in low-density forests in sunny spots and moist soil and usually occurs at low density. It is  most common in the woodland, country lanes, and garden areas of Norway, Sweden and UK.

Abundance although dipping between 2006 and 2015 as many species did  due to a dip in temperatures was followed by a rapidly increasing trend with a run of warm years from 2017 with 2022 and 2023 being exceptional. An interesting contrast is  when Small Tortoiseshell boomed in the wet summers of 2020-21  Comma dipped to half  but then in the hot & dry early summers of 2022 and 23 Tortoiseshell collapsed while Comma boomed. What was the link?  We know that both Comma and Red admiral caterpilars are not only singular but also hide underneath leaves and make tents while gregarious caterpillars like the other vanessids who thermoregulate by getting closer together  may overheat in full sun.  In contrast Comma and Red admirals whose  singular larvae are at ambient temperature benefit a great deal more from a warming climate

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).