The fine weather earlier this week – at the end of March 2021 – saw the emergence of some butterflies, Peacocks and Small Tortoiseshells, from their winter hibernation. Although they are hunkered down somewhere over the cold months, you would probably never find them (unless they are inside the trunk of an old tree), as they nestle down deep in a patch of vegetation, their wings closed so that they blend in perfectly with the background (see below).
Both Peacock butterflies and Small Tortoiseshells enter hibernation in late summer or early autumn, and emerge again in the Spring. It used to be said that these overwintering adults first appeared in April (Dennis, 1985), but with climate change and good weather, their emergence probably occurs much earlier now. Anyhow, we were blessed with a warm spell, temperatures reached about 20 deg C in Scarborough (North Yorkshire) on 31 March 2021, when these photos were taken; much higher for a butterfly basking in the direct sunshine of course.
The butterflies were making the most of the warm weather: feeding, setting up territories and tying to mate. This generation will give rise to a new brood in June or July, probably. Below is a nice fresh specimen from the same area on 17 July last year (2020).
In both of these species, the males set up territories in the afternoon, which they occupy and defend for a few hours – about 1 h 30 min in Aglais urticae and about 4 h in Aglais io, according to Baker (1972) – flying up to intercept any other butterfly, hoping it is a female. Both species occupied a number of different patches: dried up bracken, emerging nettles (below) and grass with dandelions.
The Small Tortoiseshells were more abundant, and in one patch I came across some courting pairs. Mating in this species seems to be something of a waiting game. The male – which is generally smaller than the female – flies up and positions himself just behind the female (see below).
Whilst sitting behind the female, the male “drums” his antennae on the hindwings of the female; perhaps he is tasting the cuticular hydrocarbons on her body surface, or maybe he is just letting her know that he is there! This antennation, as it is called, is said to make a feint sound that is audible to the human ear (British Butterflies), but maybe I am too deaf to hear it!
Anyway, the male carries on sitting behind the female as she is nectaring and may follow her for while, but probably not out of his territory. Apparently, this can go on for several hours – a testimony to the persistence of the male. The female may in fact be selecting the most persistent, and hence vigorous male, in this way.
Eventually, the female may allow a male to mate with her, if she has not already mated, but this is rarely observed, and certainly not by me. Below is a nice video of a male Small Tortoiseshell getting a little bit closer to the female than the one in my photos.
Baker, R. R. (1972). Territorial behaviour of the nymphalid butterflies, Aglais urticae (L.) and Inachis io (L.). The Journal of Animal Ecology, 453-469.
British Butterflies: Small Tortoiseshell: https://www.ukbutterflies.co.uk/species.php?species=urticae
Dennis, R. L. H. (1985). Voltinism in British Aglais urticae(L.)(LEP.: Nymphalidae): Variation in space and time. In PROC. TRANS. BR. ENTOMOL. NAT. HIST. SOC. (Vol. 18, No. 2, pp. 5-61).