Body width, body length and number of antennal segments allow good discrimination between teneral individuals of the instars of S. sacchari.

Nitrogen levels in commercial plots of sugarcane varied over the cane-growing season. However, when adjusted for seasonal effects, nitrogen did not have a detectable effect on the size of mealybug populations on cane. In laboratory experiments, the survival of immature Saccharicoccus sacchari and the size attained at the onset of the oviposition period was influenced by the level of nitrogen fertiliser applied to potted sugarcane. Survival of S. sacchari increased to a maximum at 320 mg L-1 soluble nitrogen in sugarcane and decreased at higher levels, while size increased with increased nitrogen over the whole range of concentrations tested. Nitrogen-driven changes in the abundance of S. sacchari predicted from laboratory data indicate that normal variations in nitrogen concentrations of field-grown sugarcane have little effect on the population dynamics of S. sacchari.

Generation time of S. sacchari females reared on potted cane ranged from 107 days at 20-degrees-C to 25 days at 30-degrees-C. Three models were fitted to developmental data. The linear model indicated a minimum threshold temperature of 17-degrees-C and the inverse polynomial model a maximum development rate at 30.4-degrees-C. Developmental response to temperature varied from that previously reported in Egypt and the Philippines. The largest and most fecund females were produced at 30-degrees-C. Net reproductive rate varied from 82.0 and 79.7 at 20 and 33-degrees-C respectively to 205.5 at 30-degrees-C. The intrinsic rate of natural increase (r(m) increased from 0.038 at 20-degrees-C to 0.186 at 30-degrees-C. The value of the common shape parameter of the Weibull distribution used to describe adult survivorship curves was 3.5, indicating type I survivorship curves. The ovipositional threshold (V0) was estimated as 16.5-degrees-C. The rate of development of individuals had a major influence on fecundity, both directly and indirectly, through adult female size and the duration of the oviposition period. The ability of S. sacchari to produce large individuals with high fecundities when corresponding rates of development were highest give this tropical species a capacity for rapid population growth at high temperature.

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.