As far as is known, females of J. evagoras mate only once. Nevertheless, males routinely inspect and attempt to mate with older females that reject them by turning towards them and vigorously fluttering their wings. Given the frequency with which this behaviour is observed, it is reasonable to suspect that harassing males are sometimes successful in achieving second matings, or in finding unmated females in this manner. However, older females, as estimated from wing wear, have been observed mating on only a very few instances over all the years that the species has been studied in the field, and none of the females that has been dissected has ever contained more than one spermatophore (Hill and Pierce 1989). It seems likely that not all females are mated upon eclosion, and thus selection favors males that constantly patrol the mating status of adult females. Individual males can mate more than once, but time of eclosion, relative size and longevity are all critical components of male lifetime reproductive success (Elgar and Pierce 1988). Shortly before the emergence of the adult, a pupa of J. evagoras secretes volatile chemicals that attract males. This can be demonstrated dramatically by crushing a pupa that is about to eclose: males are attracted to alight upon fingers coated with compounds from the crushed pupa. Males cluster around pupae waiting for a female to emerge; once she has emerged the males engage in a vigorous competition for mating and it is not uncommon for a male to commence mating immediately, even before the imago has fully expanded and dried her wings (Pierce et al. 1991). But perhaps the most curious aspect of this mating display is that males do not appear to be able to distinguish between male and female pupae, and will hover about a male pupa until the adult emerges and then discover their mistake through trial and error.

Information sourced from:

Pierce, N. E. and Nash, D. R. 1999. The Imperial Blue, Jalmenus evagoras (Lycaenidae). In: Monographs on Australian Lepidoptera Volume 6. Biology of Australian Butterflies (eds. R. L. Kitching, E. Scheermeyer, R. E. Jones and N. E. Pierce) pp. 279-315. CSIRO, Melbourne.

References cited:

Elgar, M. A. and Pierce, N. E. 1988.  Mating success and fecundity in an ant-tended lycaenid butterfly.  Pages 59-75 in Reproductive Success: Studies of Selection and Adaptation in Contrasting Breeding Systems (T. H. CluttonBrock, ed.).  University of Chicago Press, Chicago.

Hill, C. J. and Pierce, N. E. 1989. The effect of adult diet on the biology of butterflies 1. The common imperial blue, Jalmenus evagoras. Oecologia 81: 249-257.

Pierce, N.E., Nash, D.R., Baylis, M., and Carper, E.R. 1991. Variation in the attractiveness of lycaenid butterfly larvae to ants. Pp. 131–143. In: Cutler, D. and Huxley, C. (eds) Ant–plant interactions. xviii + 601 pp. Oxford University Press, Oxford.