There is a huge diversity of different courtship behaviour in butterflies, but one feature appears to be universal: female butterflies ‘almost never fly towards males to mate’ (Scott, 1973). In other words, male butterflies nearly always initiate courtship. For example, in the common blue butterfly (Polyommatus icarus) this involves a display of fluttering wings – but the sequence is often terminated prematurely in the face of female indifference or refusal and very often does not proceed as far as copulation. The male butterfly cannot force himself upon a female; there is always an element of choice by both sexes.

For butterflies, the process of finding, recognising and attracting a mate usually rests on a combination of sight and scent (Vane-Wright and Boppré, 1993). In general, male butterflies are notoriously poor at recognising potential mates at a distance, but once a male is close to a female however, it is thought that he can distinguish between small differences in wing colour marks and patterns. The males of some species have very specific preferences in terms of female wing colouration (e.g. Imafuku and Kitamura, 2015).

Courtship behaviour in blues (or lycaenids) often follows an established pattern; for example, the following sequence is based on that of the Xami Hairstreak, Callophrys xami (Lycaenidae), a beautiful little green-tinted lycaenid found in Mexico and Texas. (Taken and adapted slightly from Cordero, 1993):

1. A female flies close (< 1 m) by a flying or, more likely, perching male.
2. The courtship flight. The male flies closely behind the female, parallel to the ground, for 30 secs or so.
3. The pair alight on vegetation close to each other.
4. The male walks in front of the female, facing her head to head on whilst fluttering vigorously and it is thought, emitting pheromones.
5. The male takes up a parallel position beside the female, still fluttering his wings.
6. The male moves the tip of his abdomen to make genital contact with the female, stops fluttering. The pair commence copulation, adopting the ‘tail to tail’ in copula position.
7. The female start to walk and the pair eventually separate and fly away.

The release of pheromones is a crucial element in courtship and the effect is to increase the receptivity of the female and make her more likely to accept the male. Key aspects of the courtship are carried out by the male with the aim of bringing his pheromone-emitting structures into contact with the female, so that she can receive the chemical messages they convey. For courtship to progress, the female must respond positively to the bouquet of chemical signals (the pheromones) released by the male when he comes close to her. This is the fluttering phase. His courtship serves to increase her receptivity. It is thought that the pheromones produced by the male provide signals containing a wealth of information by which females can determine his health and status – and hence his desirability. In this way she can make her choice from the pool of available suitors.

The following photos shows a segment of courtship behaviour in Lang’s short-tailed blue (Leptotes pirithous). Whether the pair encountered each other whilst flying, or whether a patrolling male came across the female sitting in the vegetation (more likely) I don’t know. I was first attracted by the fluttering of the male; I just managed to grab these few photographs before they flew off. The photos were taken in Galicia, Spain, on 18th Aug 2017.

The sequence starts with the female attached to a sharply pointed gorse leaf (above and below). Her wings are open and folded downwards somewhat. The male is situated slightly below her and his wings are open and horizontal. The left hind-wing of the female is either damaged or not properly unfolded. Could she have just emerged from her pupal case? Mating often takes place shortly after a female has eclosed.

The butterflies are moving about slightly with respect to their relative position. I also moved to get a better shot from above.

In the next shot (below) the male appears to be positioning himself underneath the female.

In the next two shots, the female appears to be moving away from the male, inching up towards the point of the gorse leaf. The male’s wings are closed in the second photo (below), showing that he is fluttering.

In the following sequence the female has closed her wings. It is important to bear in mind that they both may have opened and closed their wings multiple times between photographs.

In the final shot (below) the male has moved above the female. This probably marks the end of the courtship, which ended soon afterwards. Perhaps I had disturbed the butterflies too much. Or perhaps this was just one of those ‘getting to know you’ type of interactions which ended without mating. It would be inappropriate to say that it was unsuccessful. The butterflies flew off. This was just one of the many courtship events which did not terminate in copulation. Perhaps they were just not right for each other? Or did the presence of a lumbering humanoid put them off?! N.B. I shot this sequence without the use of a flash. The images would probably have been improved with fill-in flash, but the apparatus is more cumbersome for this type of photography.

These photographs were taken on a rather cool and overcast day. On warmer days butterflies are more active and it is sometimes more difficult to capture interesting behaviour when they are flying about and moving very quickly. This blog is a rather crude attempt at capturing courtship behaviour, or a segment of behaviour, with a still camera. Much more could be achieved with video, particularly the slow-motion videos we sometimes see on the best nature programmes on TV.

References

Cordero, C. (1993). The courtship behavior of Callophrys xami (Lycaenidae). J Res Lepid, 32, 99-106.

Imafuku, M., & Kitamura, T. (2015). Ability of males of two theclini species (Lepidoptera: Lycaenidae) to discriminate between sexes and different types of females based on the colour of their wings. European Journal of Entomology, 112(2), 328.

Scott, James A. (1973). Mating of butterflies. J. Res. Lepid 11, no. 2 (1973): 99-127.

Vane-Wright, R. I., & Boppre, M. (1993). Visual and chemical signalling in butterflies: functional and phylogenetic perspectives. Philosophical Transactions: Biological Sciences, 197-205.