It is a widely held concept that the pheromone matrone acts to prevent a second insemination during the entire life of fully inseminated females of Aedes aegypti. We have demonstrated that females of the ROCK strain, inseminated at 4 days post emergence, which become chronologically old (28 days) but remain physiologically young by being denied blood, cannot be inseminated a second time. In contrast, some fully inseminated females which through the ingestion of human blood progressed through a number of gonotrophic cycles, becoming physiologically older, were inseminated a second time. Within groups of 100, second insemination occurred in 6% following the 4th cycle, 22% after the 5th, 38% after the 6th and 48% after the 7th.
