Mating greatly increases the oviposition rate of female Cecropia silkmoths. 2. Implantation of the spermatheca from a mated female (either with or without sperm) into a virgin female did not alter the typical virgin oviposition pattern. 3. After implantation of the bursa copulatrix (minus the spermatophore) from a mated female, the virgin female oviposited eggs in the typical mated pattern. 4. Similar implantations of bursae from virgin females or from females which had mated with castrate males did not alter the virgin oviposition pattern. 5. Injections of hemolymph from mated females into virgin females caused an increase in oviposition rate. Blood from virgin females had no effect on oviposition. 6. Thus, the change in oviposition upon mating is due to a blood-borne factor which is secreted by the bursa copulatrix after contact with sperm or other substance from the testis. This bursa factor most probably acts to trigger the release of the oviposition-stimulating hormone from the intrinsic cells of the corpora cardiaca.
