The age-composition of biting mosquito populations according to time and level: a further study

Abstract

The age-composition of mosquitos biting at different times and levels was investigated in Zika Forest, Uganda. The four species studied were Mansonia aurites (Theo.) group (material mainly of actual M. aurites (Theo.) but probably including some examples of M. microannulata (Theo.)), Aedes africanus (Theo.), A. ingrami Edw. and Culex annulioris Theo. In each case the biting cycles of nulliparous and parous females were computed separately.The material examined came from eleven 24-hour catches made by Dr. A. J. Haddow. Samples were taken at seven levels, at 20-ft. intervals, from the ground to a height of 120 ft. The top of the canopy was at 70–80 ft.In each species the biting cycles of nullipars and pars were closely similar, both at the preferred level and at all levels combined. In only one case (that of the group of M. aurites) was there a significant and consistent difference in the average age of females at different levels, there being a relative excess of older females above the canopy, as found previously in M. fuscopennata (Theo.). This difference persisted throughout the period of biting activity.These and other recent findings are briefly discussed. It is concluded that the hypothesis which relates the form of the mosquito biting cycle to the age-composition of the biting population and to the larval habitat of the species concerned cannot be accepted as a valid generalisation.