Determination of physiological age in anophelines and of age distribution in anopheline populations in the USSR.

Abstract

A technique is described whereby it is possible to make an accurate determination of the physiological age of anopheline females, i.e., the number of gonotrophic cycles through which the female has passed. This technique is based on counts of the dilatations left in the ovarioles subsequent to each maturation of follicles and oviposition. The number of dilatations found on dissection usually corresponds exactly to the number of gonotrophic cycles.By dissection of a large number of female anophelines the age composition of the mosquito population and any changes of it in the course of the transmission season may be determined, and a number of problems of population biology may be elucidated. With a knowledge of the temperature in mosquito shelters, it is possible to establish the number of gonotrophic cycles coinciding with a single sporogonic cycle of the malaria parasite and thus the physiological age at which the salivary glands of females may contain sporozoites. Dissection also makes it possible to determine the proportion of potentially dangerous females at various periods of the season. The data thus obtained are used in drawing up an epidemiological picture of a locality and in evaluating the effectiveness of anti-malaria measures.A simple technique is also described for distinguishing between parous and nulliparous female anophelines by examination of the tracheoles of the ovaries.