Survival and Development of the Immature Stages of Culex annulirostris (Diptera: Culicidae) at the Ross River Dam in Tropical Eastern Australia

Abstract

Immature stages of Culex annulirostris Skuse from Ross River Dam were reared in the laboratory at constant temperatures (18.0, 24.5, 28.5 and 35.0 degrees C) and in the field in the presence or absence of predators. In the laboratory, survival from first instar to adult emergence increased from 5.5% at 18 degrees C to 96.5% at 35 degrees C. In the field predators increased mortality by almost 60%. Adult wing length increased inversely with constant temperature except at 18 degrees C. In the field the largest adults were produced in the presence of predators. The developmental threshold temperature (to) and thermal constant (K) were estimated from laboratory data to be 13.7 degrees C and 129.3 DD, respectively. K determined in the laboratory did not differ significantly from that required in the field (132.8 and 153.5 DD above 13.7 degrees C in the presence and absence of predators). Numbers of immature Cx. annulirostris at four sites in the dam rose to a peak after four or five generations and then rapidly declined. Overall survival of immatures was very low but was significantly higher at the one site where Melaleucas also occurred. Age-specific survival was highest in the first instar. Estimated survival from hatching to eclosion ranged from 4/1,000 to 185/1,000. Mortality appeared to be density independent and was attributed mostly to predation.