Flying populations of Culicoides (Diptera: Ceratopogonidae) were sampled in four different traps. Sampling was conducted at two different sites (Amberley and Churchbank Weir) in south east Queensland over a period of nearly two years.
Twenty four species of Culicoides were collected, totalling more than 130 000 specimens. C. austropalpalis comprised more than 68% of this total.
Catches of the three most abundant species (C. austropalpalis. C. brevitarsis and C. marksi) were subjected to detailed statistical analysis. Catches were transformed to logarithms and regressed on meteorological variables. The magnitudes of the partial regression coefficients were found to be strongly correlated with the mean catch of midges in the analysis. Conclusions based on the magnitudes of the partial regression coefficients were thus not justified.
All species were found to become more abundant with increasing temperature, decreasing wind speed, cloud cover and some sexes and species were less abundant at high dew point. At one site only, one species was more abundant with moonlight, while at the other site, another species was more abundant in absence of moonlight. Although light trap catches fell with increasing illuminance, truck trap catches indicated peak activity at twilight illumination levels, and reduced activity at higher or lower illuminance. The effect of cloud cover on catch, at one site only, was such that less insects were caught under a partially cloudy sky than clear or overcast skies. C. austropalpalis at Amberley appeared to show a lunar cycle, with reduced catch at full moon, while C. brevitarsis at Churchbank Weir showed a lunar cycle with reduced catch at new moon. These effects were not observed in the results from the alternate sites. Most of the daily cycle of abundance can be explained by the effect of diurnally synchronised meteorological variables, but there appears to be a weak residual daily cycle, with crepuscular peaks, in C. austropalpalis.
The correlation of partial regression coefficients with mean catch indicates a serious failure of either the transformation or the applicability of multiple regression analysis to the data. Due to this difficulty in the analyses, few of the initial goals of the study have been met with quantitative information.