This mechanism is also known as arrhenotokus parthenogen-esis. It is a common mechanism in several insects such as ants, bees and wasps. In these insects, fertilized eggs develop into diploid females and unfer-tilized egg into haploid males.
In a honey bee colony a queen bee can lay two types of eggs. They are the fertilized and unfertilized eggs. It happens by controlling the sphincter in the sperm receptacle of the female. The diploid female zygote can develop either into a queen or a sterile female worker bee. The sterile nature of the worker bee is due to poor nourishment. The haploid zygote de-velops into a male. This mechanism of sex determination helps to maintain the polymorphic nature in a honey bee colony.
Apart from genetical systems, the sexuality can also be con-trolled by various factors such as metabolism, environment and hormones.
Bonellia viridis is a marine worm. Its sex determination was studied by F. Baltzer(1935). The adult female worm is about 2.5 cm long. It has a well defined anatomical organization.
The male is very small and microscopic. Its body organs are rudimentary. The males normally live as parasites attached to females. All larvae of Bonellia are genetically similar. However a larva settling on the proboscis of an adult female becomes a male individual. If a larva develops in isolation (ie., in the absence of a female) it develops into female. If a develop-ing male is detached from the proboscis of female, it becomes an intersex. From these observations it could be inferred that the proboscis of adult female secretes some hormone like substance and that substance suppresses female-ness and induces maleness in the larvae which remains attached.