Imperial-blue2.JPG (28212 bytes)Common Imperial Blue Butterfly: is known scientifically as Jalmenus evagoras. The species isImperial-blue1.JPG (30525 bytes) found in southern Queensland , eastern New South Wales , Australian Capital Territory and eastern and central Victoria . The Common Imperial Blue is said to be common but local.
Adults have a pale, metallic, greenish-blue central area in the wings. The hindwing has two orange-red spots and fine, black tail. When the butterfly is resting the tail, at the base of each wing, moves in the wind rather like an antenna. It is thought that this movement may deceive predators into attacking the tail rather than the butterfly's head.  "Tis better to lose a tail than to lose one's life". Lizards adopt the same survival strategy. 
The Common Imperial Blue feeds on many species of Acacias (Wattles). In the illustrations the larva is feeding on Acacia parvipinnula foliage. The larvae are pale and speckled at first and become reddish brown or green with outgrowths on the body known as tubercles. Each body segment has a pair of fine white diagonal lines.
The pupa is shining black with some orange-brown markings. Pupae cluster together along the stems of food plants.
The most noticeable feature of this butterfly is the presence of large numbers of small black ants. These belong to species of the Iridomyrmex. The ants protect the larvae and pupae from predators. In return the ants are rewarded by nectar that is secreted from the bodies of larvae and pupae.
Newly emerged males are rather eager and fly around the unopened pupae waiting for emerging females. Mating often takes place before the wings of emerging females have had time to expand.
The photos were taken at Yallaroo. The photo on the left is an adult resting on the food plant. The one on the right is a mature larva just before pupation. This photograph also shows the guardian ants.
Acacia parvipinnula is a suckering Wattle and at Yallaroo many small plants surround a grove of mature specimens. Only one small plant played host the larvae. Our attention was drawn to the plant by an adult butterfly fluttering around. We only observed one butterfly.
The pupae seem to develop rapidly. Two or three weeks after pupation the pupae cases were empty.
In the future we will be paying close attention to our Wattles and hope that these interesting insects return.  
The only other time we have observed the Common Imperial Blue and their hordes of attendant ants was in the Blue Mountains, west of Sydney , over 40 years ago.