Age determination of Aedes cantans using the ovarian oil injection technique

A study of the age structure of a population of adult female Aedes cantans Meigen was undertaken using the ovarian oil injection technique to determine parity. Results showed that, contrary to popular opinion, ovariolar sacs do not form gonotrophic dilatations and cannot be used for physiological age determination. Dilatations were formed only by follicles which degenerate at a very early stage in the gonotrophic cycle. The proportion which consistently do degenerate (the gonotrophic diagnostic index) decreases in each successive cycle. Results showed that the mean age of the population during the study was 2.04 parous, which was one gonotrophic cycle less than expected, possibly due to scarcity of hosts in the area.