Most species of insects are of two sexes, but in some--the white-fringed beetle, for example--males are unknown. In certain insects the sex of the offspring depends upon whether or not the egg has been fertilized. The unmated females of some parasitic wasps produce males only, while mated ones produce the two sexes in about equal numbers. The queen honeybee can lay either fertilized or unfertilized eggs, according to the needs of the hive. Unfertilized eggs produce drones, while fertilized eggs produce females.
The adult female instinctively places her eggs in a place suitable for their hatching and for proper development of the young. Parasitic wasps and flies place their eggs directly on the host. The horse botfly glues her eggs to the hairs of the horse where they can be licked off and thus be transferred to the horse's stomach; the larvae live on the lining of the stomach and intestines.