BY EXAMINING THE OVARIOLES BY

The recognit ion of nul l iparous and parous mosquitoes is impor tant in relation to survival rates of mosquitoes and the epidemio logy of malar ia (MACDONALD, 1957), and in the study of the bit ing t imes of young and old mosquitoes. Examinat ion of a number of Anopheles gambiae showed that nul l iparous and parous indiv iduals could be recognized by means of the funicles of the ovaries (LEwis, 1957, 1958), and it is hoped that this method will prove to be appl icable to larger numbers of var ious species. METHODS The mosquitoes used came from a Ross Institute Laboratory colony of A. gambiae from Northern Nigeria. About 25 nulliparous females, and 25 parous ones which had laid once, were examined. A little normal saline containing 1 per cent. of liquid detergent (Quix, a domestic brand) was pipetted into the tube containing each mosquito which was immediately wetted and drowned, and was removed to a drop of saline without detergent on a slide. When the ovaries were small the head was removed, the abdomen icked near the tip, and the ovaries and other viscera, usually, drawn out backwards. When the ovaries were large the abdomen was separated from the thorax, the tip of the abdomen was removed, and the ovaries were freed by inserting afine needle-scalpel into the abdome