A series of forty 24-hour catches was carried out at seven levels (20-ft. intervals from 0 to 120 ft.) on a steel tower in Zika Forest by means of unbaited and unlighted suction traps that acted simply as air samplers. The object was to study the general flight activity of mosquitos in a tropical forest environment from samples that would not be subject to the selective effects exercised by bait-traps and light-traps.Altogether, 4,151 mosquitos belonging to thirty-four species or species-groups were taken. Eight species, Aedes (Stegomyia) apicoargenteus (Theo.), Mansonia (Coquillettidia) aurites (Theo.), M. (C.) fuscopennata (Theo.), M. (C.) maculipennis (Theo.), M. (C.) metallica (Theo.), M. (C.) pseudoconopas (Theo.), M. (Mansonioides) africana (Theo.) and M. (M.) uniformis (Theo.), were taken in numbers sufficient for detailed analysis. By far the most abundant of these was M. aurites, comprising 55·7 per cent, of the total sample. The remaining twenty-six species together constituted only 7·6 per cent.Only 144 or 3·5 per cent, of the mosquitos taken were males; and of the females, only 19 or 0.5 per cent. were blood-fed and only 11 or 0·3 per cent, were gravid. Thus, catches in the suction traps consisted almost entirely of unfed non-gravid females. It is tentatively concluded that male mosquitos in the forest are generally very inactive in the absence of stimuli such as lights or baits. The paucity of engorged and gravid females was expected; few of these would come within range of the unlighted unbaited suction traps.Dissection of 3,072 females belonging to the eight most numerous species showed all to be inseminated. Age-composition was determined in species of Mansonia only; the majority of females in the subgenus Coquillettidia were nulliparous, whereas in the Mansonioides, nulliparous and parous females occurred in roughly equal proportions.The unlighted, unbaited suction traps caught far fewer mosquitos than did light- and bait-traps under similar conditions.In general, the vertical distributions and flight-activity cycles of the various species as indicated by the suction-trap catches differed distinctly from those indicated by bait- and light-trap catches reported by other workers. Very little activity was recorded above the forest. Although, in general, activity was irregular, three main patterns could be distinguished: largely nocturnal activity continuing up to about midday but almost completely suppressed in the afternoon, as in M. aurites, M. fuscopennata, M. maculipennis, M. metallica and M. pseudoconopas; activity spread throughout the entire 24-hour period, as in M. africana and M. uniformis; and mainly diurnal activity, as in A. apicoargenteus.
Local variation in cereal aphid flight activity in Canterbury
