Butterflies of Thailand, Malaysia & Borneo
Eumolphus Oakblue
Arhopala eumolphus   CRAMER, 1780
subfamily - THECLINAE
Arhopala eumolphus, female, Ulu Gerok, West Malaysia   Adrian Hoskins
It is unclear how many species should be classified within the genus Arhopala. Some consider that the genus should only include a few Papuan species and place all other related species in Panchala, Narathura or Aurea. Here I follow the classification adopted by Corbet & Pendlebury, who include all these genera within Arhopala. Thus defined the genus is widespread, with various species found from Afghanistan to Japan, and south across the Pacific to Australia. In total there are over 220 species, collectively known as Oakblues.
The undersides of all species are earthy brown, and bear a complicated pattern of dark spots and blotches, usually edged in whitish.
Distinguishing the species is very difficult, and best achieved by reference to the keys and genitalia illustrations in Corbet & Pendlebury.
In Malaysia there are at least 110 species, most of which are some shade of metallic blue or purple on the upperside, although there are several iridescent green species including aurea and trogon.
Arhopala eumolphus is one of several species which the males are metallic green above, but the females are blue. It occurs from Myanmar to Java.
This species is one of the commoner Oakblues in peninsular Malaysia, and occurs in primary forest habitats at altitudes between sea level and about 600m.
The lifecycle has been studied, but the larval foodplant has not been identified. Arhopala species use a wide variety of foodplants including Quercus ( Fagaceae ), and various species of Myrtaceae, Combretaceae and Lythraceae.
The egg is laid singly on the underside of a mature leaf, and is white, with a reticulated network of ridges. Often several eggs can be found on one leaf, probably laid by the same returning female.
The caterpillar hatches after about 2 or 3 days, and partially eats its eggshell before moving away to find a fresh young leaf, in which it nibbles tiny holes. When fully grown it is oval in shape, slightly flattened, and pale translucent green in colour with a prominent creamy dorsal line. It is attended by the ant Polyrachis which milks it to obtain sweet secretions exuded from it's dorsal honey gland.
The chrysalis is formed on the underside of a leaf, and is pale brown, speckled with dark olive dots.
Adult behaviour
Oakblues of both sexes tend to spend most of their time sitting motionless on the foliage of trees and bushes, at a height of about 2 - 5 metres. They are not known to visit flowers, and males do not appear to come to the ground to imbibe mineralised moisture. It seems likely that both sexes obtain their sustenance from aphid secretions on leaves and twigs.


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