Jalmenus evagoras is multivoltine, with two broods commonly found in the south, and three or four in the north. Overwintering occurs in the egg stage. Males and females show little sexual dimorphism in wing colour or pattern. However, female pupae are larger than male pupae, and adult females can be as much as 60% heavier than adult males. For example, at a field site in Mt Nebo,Queensland, females weighed 72.2 ± 30.4 mg (Mean ± SD; N = 42), whereas males weighed only 45.7 ± 17.3 mg (N = 52 ) (Elgar and Pierce 1988). The species is protandrous, with males eclosing several days before females. The sex ratio of individuals raised from eggs in the laboratory is 50:50 (N.E. Pierce, unpublished observations). However, because of protandry and the considerable difference in male and female survivorship, the effective sex ratio in the field is usually strongly male biased (Elgar and Pierce 1988; Costa et al. 1996). Adult J. evagoras fly from late October or November to April, while immature stages are most common in October and early February near Sydney. Eggs laid towards the end of the season, from late summer onwards, remain dormant over winter, hatching in the following spring. Eggs laid by adults of the spring generation hatch relatively quickly and produce the second generation of aduls in about two months. In captivity at 28ºC, larval development on average takes four weeks but may be shortened by as much as five days by the presence of the attendant ant (Pierce et al. 1987). Duration of the pupal stage under the same conditions is about seven days irrespective of ant attendance. Adults generally fly within a few metres of the ground, and usually do not venture far from the breeding areas. They readily feed from flowers, including those of Bursaria spinosa (Pittosporaceae), and it has been demonstrated that sugar in the diet of adult females significantly increases their longevity, thereby increasing their reproductive potential (Hill and Pierce 1989).

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.

Braby, M. F. 2000.  Butterflies of Australia: Their Identification, Biology and Distribution.  CSIRO Publishing, Melbourne.

References cited:

Costa, J. T., McDonald, J. H. and Pierce, N. E. 1996. The effect of ant associations on the population genetics of the Australian butterfly Jalmenus evagoras (Lepidoptera: Lycaenidae). Biological Journal of the Linnean Society 58: 287-306.

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., Kitching, R. L., Buckley, R. C., Taylor, M. F. J. and Benbow, K. F. 1987. The costs and benefits of cooperation between the Australian lycaenid butterfly, Jalmenus evagoras, and its attendant ants. Behavioral Ecology and Sociobiology 21: 237-248.