Oviposition by exophytic dragonflies on vehicles

Odonata that lay exophytically may. at times, oviposit on dry surfaces. In some cases this behaviour is linked with hatching that is delayed until the surface is flooded (PS. CORBET, 1962, A biology of dragonflies, Witherby, London), In others, oviposition appears to be triggered by smooth surfaces (e.g. concrete, vehicles) that might simulate the appearance of water (R. ROWE, 1987, The dragonflies of New Zealand, Auckland Univ. Press, Auckland; J.A.L. WATSON & A.F. O’FARRELL, 1991, The insects of Australia, 2nd ed. Melbourne Univ. Press, Melbourne). A recent example in this second category has involved significant damage to new motor vehicles in Darwin, Northern Territory, Australia. At the end of the wet summer in northern Australia large numbers of Odonata emerge from the shallow, warm and productive waters of the floodplains (J.A.L. WATSON, 1980, Habitat 8(4): 3- 5). Some disperse far from water, including the libellulids Macrodiplax cora (Kaup in Brauer), Pantala flavescens (Fabr.) and Trapezostigma loewii (Kaup in Brauer), and form vagrant flocks, often behaving as ’fliers’ rather than ’perchers’. The ’Wet’of 1990-91 was the wettest ever recorded in Darwin and the flocks of dragonflies were, it was reported, unusually abundant. Problems arose when the females laid their eggs on the shiny horizonal surfaces of new vehicles, especially pale ones, at a vehicle-importer’s yard in Darwin. The egg masses took the form of stripes, correlating with the oviposition patterns of Pantala and at least some species of Trapezostigma, the females of which lay while flying forward in or out of tandem (J.G. NEEDHAM H.B. HEYWOOD, 1929, A handbook of the dragonflies of North America, Thomas, Springfield and Baltimore; ROWE, 1987). Unfortunately, no specimens of the adults were obtained, nor could dragonfly eggs removed from the vehicles be identified. Corbet in ROWE (1987), however, reported that Pantala sometimes lays on motor cars.