Marsh fritillaries, Euphydryas aurinia (Lepidoptera: Nymphalidae), are one of my favourite butterflies. The beautiful tapestry of yellow, orange and black colours on their wings creates a stunningly attractive pattern, especially when contrasted against the bright pink colour of a flower.
The beautiful appearance of butterflies is, I think, even more attractive when we discover something about their lives. The subtleties of colours and behaviours are enhanced, I would argue, by an understanding – however basic, of their biology and life histories. Marsh fritillaries emerge every Spring, but they only pass through one generation as adults, before returning to an alternative existence, as eggs and larvae, to last out until they emerge again as adults, the following year.
The males usually emerge some 3-6 days before the females and generally outnumber them, at least in terms of active individuals. So when the females do appear, they are subjected to the attentions of amorous males, wishing to mate.
Butterfly biologist Manuela Pinzari and her colleagues from the University of Rome (Università di Roma Tor Vergata), have spent many years studying Marsh fritillaries, both in the laboratory and in the field, in Italy.
Courtship in Euphydryas species is often very brief, or virtually non-existent (Cannon, 2019) and the Marsh fritillary is no exception. The variety of Marsh fritillary they studied is E. aurinia provincialis (Nymphalidae) of the Italian region Latium. Their work has revealed a surprising wealth of information about the courtship and mating of these butterflies, as a result of painstaking observations and investigations. For example, they analysed over 24 hours of video recordings, cataloging the courtship and mating behaviour. I describe some of their results below. I think it almost certain that their findings apply to all subspecies.
According to Pinzari et al. (2019), virgin females do not usually put up any kind of resistance, and accept the male after a simple courtship. When a pair meet, the male immediately attempts to copulate by clasping the female genitalia, and – assuming the female does not fly off, the pair join up and remain in copula for up to four hours (copulation time in 11 pairs ranged from 1 h 45 min to 6 h 37 min).
Some virgin females may exhibit ‘initial mild refusal’ behaviour in the form of what the researchers described as Small Wing ﬂuttering (SWf), where the female slightly opens and vibrates her wings, but this does not deter the male and a second attempt at copulation is usually successful. [N.B. the genitalia structure (sterigma), changes in the mated females, the sterigma is exposed after copulation (see Fig. 7 in Pinzari et al., 2019)].
Marsh fritillaries are essentially monandrous, meaning that most females usually only mate once. Once reason for this is that during copulation the male secretes a small mating plug (or sphragis) which acts as a sort of chastity belt, with the aim of preventing further matings from occurring (see below). However, in practice, these mating plugs are not always 100% effective and some females do mate more than once. The mating plugs certainly do not put off males from trying to mate again; persistence pays off it seems!
However, it is not usually to the female’s advantage to mate more than once; she would probably be better off spending her time looking for suitable host plants on which to lay her eggs. However, it seems that persistent males sometimes manage to overcome a female’s reluctance to remate, and this is when the more interesting behaviour occurs. Pinzari et al. (2019) describe second copulation in this species as occurring as a result of a struggle ‘between persistent males and reluctant females’.
When approached by a male, an already mated female can display a range of behaviour – see Pinzari et al. (2019) for full details – including for examples: Wide Wing ﬂuttering (flapping the wings very rapidly through up to 180-degrees) and Twirling (turning repeatedly like pirouette, whilst beating the wings very rapidly). The female can impede the approaching male by vigorous wing fluttering (below).
Most striking of all, the pair can engage in a complex series of spins and twirls which Pinzari et al. (2019) called Carrousel (can also be spelled Carousel). Amazingly, the pair may change the direction of rotation up to 35 times in a short, five second period (see diagram below). In essence, it seems to be a war of attrition between a persistent male and a reluctant female!
I must confess, I have tried to observe – and capture in photographs – courtship behaviour in the species myself, without a great deal of success. One courting pair – the male chasing the female – very demonstrably showed the perils of mating by both ending up caught in a spiders web! (see below).
I had to intervene and release them both from the web; butterflies are just to precious to leave to their own devices! However, now armed with the knowledge gained by Pinzari et al. (2019), I have gone back over some of my photograph sequences to see if I could identify some of these behaviours. I cannot be absolutely sure that they really are the behaviour in question, but it it fun to try! Which is what I have done in this blog.
P.S. There are a number of different Latin names for the Marsh fritillary butterfly: Euphydryas (Eurodryas, Hypodryas) aurinia.
P.P.S. Most of these photographs were taken in Galicia in NW Spain, where Marsh fritillaries are quite common in May-June, see here.
Cannon, R. J. (2019). Courtship and Mating in Butterflies. CABI.
Pinzari, M., Pinzari, M., & Sbordoni, V. (2019). Make it simple: mating behaviour of Euphydryas aurinia provincialis (Lepidoptera: Nymphalidae). The European Zoological Journal, 86(1), 220-232. DOI: 10.1080/24750263.2019.1629030. Open Access journal here.