Experiments have been carried out for the purpose of testing an hypothesis (OLIVlERI et al., 1970) intended to explain why females of Drosophila melanogaster do not utilise all the sperm transmitted during copulation.
According to this hypothesis, the deposition of eggs and the emergence of sperm from the storage organs occur with a certain degree of independence. For this reason the number of sperm that one female utilizes for fertilization out of the total number of sperm stored, for a given intensity of emergence of the sperm, is directly proportional to the intensity of egg deposition.
The experiments reported here have shown that: (a) females prevented from egg laying for a few days after mating lose some sperm and therefore produce fewer progeny compared with controls in which normal egg laying has been permitted;
(b) females of a stock with a low egg deposition intensity (y/y), fertilised by a sample of the same males that have fertilised control Oregon-R females, produce far fewer offspring than the controls although both types of female stored about the same number of sperms.
These results seem in agreement with the hypothesis proposed.