Butterfly of the Month - December 2022
The Imperial Hairstreak (Jalmenus evagoras evagoras) is a stunning butterfly reaching a wingspan of 32mm (male) and 37mm (female), The adult stands out by looks alone. The underside shows a warm colour, somewhat similar to very light ochre. Forewing and hindwing carry black narrow bands and markings, and are edged by brown bands, a narrow white one as well as a black outer line, The bottom corner of the hindwing shows black spots which are bordered by bright orange on the inner wing side. The hindwings end in a long tail as can be seen in the image.
The bottom corner of the hindwings’ upper side is very similar to the underside, but the fore- and hindwings’ base colour is black. A large iridescent blueish (suffused with green) covers the central areas of both wing pairs.
For egg laying adult females seem to choose or prefer those plants among the suitable food plant that show the presence of ants. Like many butterflies in the family Lycaenidae the Imperial Hairstreak is well known to have its immature stages attended to by ants, in this case by ants of the genus Iridomyrmex. During our surveys we have often observed the presence of ants, just like in the image shown, fiercely protecting eggs, larvae and pupae from predators. In return the ants receive honeydew and amino acids exuded from special glands on the larvae.
Eggs are not larger than 0.6mm in diameter. They are mandarin shaped with slightly flattened top and show intricate patterns. They are laid in clusters into cracks in bark or along crevices or indentations of host plants’ stem or branches. The start with an almost translucent orange colour but gradually turn darker to a brownish shade tinged with green. Difficult to see here because of the ants, but the dark larvae exhibit lateral bands. The pupa are shiny dark brown with orange markings at each segment.
Larvae feed on a large number of Wattles. Among the favourites here in Brisbane appear to be the Green Wattle (Acacia irrorata) and Blackwood (A. melanoxylon), but others like A. decurrens, A. disparrima, A. falcata, A. fimbriata, A. leyocalyx and A. penninervis are among them.
Open eucalypt forest is the preferred habitat type for this butterfly.
Images: KR – Karen Roberts; NS – NatureShare, CC BY 2.5au; PC – Peter Chew, Brisbane Insects; SH – Simon Hinkley, CC BY 3.0 au