Comparative bionomics of adult austrostmulium pestilens Mackerras & Mackerras and A. bancrofti (Taylor) (Diptera, Simuliidae)

Abstract

AbstractLarge numbers of adult Austrosimulium pestilens Mack. & Mack, appear about a week after floods in permanent and temporary waterways and, because of the short period when stream flow remains suitable for oviposition, mating, feeding and egg maturation take place near the river where they breed. Most flies emerge early in an outbreak and fly to mating swarms at trees beside or near the river. After obtaining a blood meal from any of a number of mammal species nearby, females return to 1–5 m tall trees at the river's edge to mature their eggs in an unusually short time of 24 h. Although this species prefers rapidly flowing water, immatures also survived in trickles remaining after floods had passed, though the resulting adults took longer to develop and were smaller than normal. The closely related A. bancrofti (Tayl.) lives in more permanent waterways and disperses away from its breeding sites soon after emerging, concentrating in highest numbers on hills as far as 10 km or more from its nearest major breeding site. Catches in CO2-baited traps were influenced by temperature, wind, light intensity and rain. Although A. pestilens bit man and many mammals, A. bancrofti did not bite any vertebrate tested. In CO2-baited traps where man was present, there were large fluctuations in the catch of A. pestilens from minute to minute, while the catch of A. bancrofti decreased steadily.