Rediscovery of the Desert Sand-skipper Croitana aestiva Edwards (Lepidoptera: Hesperiidae): Morphology, life history and behaviour

Croitana aestiva Edwards is one of Australia's most poorly known butterflies. Previously it was known from a total of eight specimens collected in 1966 and 1972 in the MacDonnell Ranges west of Alice Springs in central Australia. The species was not positively recorded for the next 35years; however, in February 2007 a population was rediscovered during targeted surveys. Subsequent biological studies were conducted from 2007 to 2010. A reappraisal of adult morphology show that four character states are unique to C.aestiva. Eggs are creamy-white and subcircular, with 21-29 longitudinal ribs. First-instar larvae are creamy-white, with a dark head capsule and prothoracic plate. Fourth- and fifth-instar larvae have a dark green medial band, a pale lateral band on each side of the body, and a distinct, highly setose, brown anal plate. The pupae are mainly orange-brown, darkening anteriorly, with a highly sculptured pupal cap. The larval food plant is the grass Neurachne tenuifolia (Poaceae), which is also endemic to central Australia. Shelters for all larvae and the pupa are among the leaf sheaths and stems near the base of the tussock. Adults are opportunistic feeders on a wide variety of nectar-producing plants, and are active throughout the day. Males use patrolling and perching behaviour to locate receptive females at a range of encounter sites, including the larval food plant and hilltops. Oviposition occurs during late morning, and eggs are laid on the upper surface of blades of the food plant. Comparison of the immature stages of C.aestiva with its congeners indicates many similarities in general morphology, but there are pronounced behavioural differences such as upward-orientated shelters.