Butterflies of
Australia
Imperial Hairstreak
Jalmenus evagoras
DONOVAN, 1805
Family - LYCAENIDAE
subfamily - THECLINAE
Tribe -
Jalmenus evagoras
Canberra, Australia
© David Fischer
Introduction
The
genus Jalmenus comprises of 11 species, all of
which are endemic to Australia. The uppersides of most species are metallic
silvery-blue, with broad suffused blackish margins, and a pair of small orange
or red patches near the tail of the hindwing. In one species
eichorni the blue colouration is replaced by
metallic green. The undersides vary, some like evagoras
having black markings while in others such as lithochroa
and icilius the markings are very pale and obscure.
Jalmenus evagoras
is found in southern Queensland, Canberra, New South Wales and Victoria.
Habitats
This species inhabits open Acacia
scrub and semi-desert habitats.
Lifecycle
The eggs are
white or pale yellow and are laid in neat rows on stems of
Acacia bushes. Immediately after hatching the caterpillars wander
until they find an ant trail. They follow this until they locate a
cluster of older caterpillars, which always have
Iridomyrmex ants in attendance.
Ants are beneficial to the larvae because they drive away
predatory insects and parasitoid wasps that might otherwise attack
them. Iridomyrmex ants have been
observed actively defending Jalmenus
caterpillars from attack by predators including spiders, mantises,
Myrmecia jumper ants and
Polistes wasps.
The larvae have a series of spiky dorsal tubercles, and are dark
green with an orange dorsal stripe and marbled with lighter tones.
They live within a communal web on a small
Acacia bush, emerging to feed periodically.
The pupae are black with orange bands between the segments, and
are formed in clusters attached to twigs. The pupae are also
attended by Iridomyrmex ants.
Experiments have shown that in
cases where ants have been denied access to the pupae
the latter have suffered up to 95% parasitism by the Chalcid wasp
Brachymeria reginia. Conversely,
pupae attended by the ants experienced zero parasitism.
Larvae and pupae have been shown able to communicate with ants
using visual, audio and chemical signals which are used to appease
the ants, which would otherwise attack and kill them.
Adult behaviour
Males aggregate in clusters of up to 20 individuals
around the pupae of females on Acacia bushes.
Both sexes nectar at Asteraceae and various flowering bushes and
shrubs.
Jalmenus evagoras
Canberra, Australia © David Fischer
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