Abstract

The catch of some noctuid pest species in a light trap operating for 18 months in south coastal Queensland was compared with the emergence of adults in cultures reared simultaneously in a field cage in the trapping area. Generally there was a good positive correlation between the monthly catch and the rearing results. In March 1973 the catch of most species observed was high despite a small emergence of adults, probably because much of the catch consisted of moths entering or flying over the area in connection with weather fronts. A lunar periodicity was found in the catch of most species but not in the emergence of adults in the cultures. Strong illumination, however, suppressed or delayed oviposition. Theoretically five to six generations a year can be expected in the area. None of the more abundant species are, however, adapted to both winter and summer conditions, and all are present in low numbers for some part of the year. If the weather during prolonged periods strongly departed from the long-term local average, the populations of different species could be more or less obliterated. This was, however, in most species compensated for by repeated reinfestations from other areas. Immigration also accounted for the sudden appearance of some species after prolonged absence. The results suggest that studies of this type may provide information on population changes caused by local conditions and population movements.