Jalmenus ictinus Hewitson
Interesting aspects: This butterfly has recently been recorded from the Broken Hill area of New South Wales, where it is known to occur in two colonies. One colony occurs in the Barrier Range north of Broken Hill, some 70 km to the east of South Australia's border with New South Wales, the other occurs 140 km east of Broken Hill.
The nominotypical butterfly from the eastern areas of Australia looks similar to Jalmenus lithochroa but is slightly larger and the underside markings are much more distinct with the markings being black rather than brown as in J. lithochroa. However, the form of the butterfly in the Broken Hill area is smaller than the nominotypical butterfly and its underside markings are brown rather than black. The butterfly belongs to the endemic Australian Theclinae, which have a very strong obligatory association with ants.
The butterflies are colonistic and usually remain very near to the colony. The males are often active as they fly about the foodplant looking for newly emerged females, but they can also spend a lot of time basking in the sun on the foliage in the higher outer parts of the hostplants. When not feeding, the females spend most of their time searching for places on the hostplants to lay eggs, by walking and testing suitable places in the foliage, branches or on the trunk, accompanied and protected by the large attendant meat-ants. However, this ant docility can quickly turn ferocious for any unwary human observer that gets too close to the colony inhabitants.
The early stages are similar to other Jalmenus species.
Larval food-host: The larvae are known to eat various Acacia species. The particular species utilised in the Barrier Range have not been determined. Of the Acacia hosts utilised further east by the butterfly, only one host is known to occur in the Barrier Range area, and this is A. pendula (Boree or Weeping Myall) (Leguminosae/ Mimosoideae). However, this species probably does not occur naturally in the area, being a homestead 'garden-escape'. The larvae eat the leaves, flower buds and galls of the host plants.
Larval attendant ant: The larvae are usually attended by large meat ants Iridomyrmex purpureus. These are large aggressive ants to 1 cm that can inflict a painful bite, but do not have a sting.
Flight period: It has been reported to fly in the Broken Hill area during October to December. Elsewhere it flies during November to March with continuous broods. The colonies over-winter as eggs.
Distribution: The butterfly is usually recorded in the higher rainfall open woodland areas along the eastern parts of mainland Australia in Queensland, New South Wales and Victoria. Its presence in the arid Barrier Range at Broken Hill in the western part of N.S.W. is therefore unusual. The Olary Range immediately to the west of Broken Hill in S.A. would seem to be analogous habitat to the Barrier Range, although more suitable S.A. habitat would probably exist in the Acacia woodlands south of Broken Hill in the SA-NSW border areas, and it is faintly possible the butterfly may be found there in the future, particularly along ephemeral creek lines. The fact that the butterfly has not been reported in the more suitable habitats of S.A. may suggest that it has a need for particular species of Acacia that do not occur in S.A. The obligatory attendant meat-ant is a common species in S.A.
Habitat: It usually occurs in temperate to cool-subtropical, higher rainfall, open woodland areas.
Conservation Status: Although widely distributed in the eastern states it tends to be rare, but can be locally common when conditions are favourable. Quite often the active colonies are stressed and suffer from disease and parasitoids.
Threats: It occurs in discreet colonies that are highly vulnerable to any detrimental process, particularly grassfires, periodic droughts and the application of aerial insecticides. Its potential habitat in the Olary and Barrier Ranges is also a prime breeding ground for the plague locust and the butterfly is likely to be decimated by any toxic spray programs adopted by the Locust Control Boards.
Author: R. GRUND, © copyright 3 August 2004, all rights reserved.