Embryogenesis

This chapter presents a generalized view of some of the more regular features of insect development. Embryogenesis is the process by which a larva or a juvenile is built from a single egg. The fertilized egg divides to produce hundreds of cells that grow, move, and differentiate into all the organs and tissues required to form a larva or juvenile. Embryogenesis is extremely diverse in different insect species. In some species, a single egg gives rise to several thousand larvae; in others, embryos devour their mothers before hatching. The most extreme variations are found among insects that parasitize other insects. Insect eggs are typically quite large, both in absolute dimensions and relative to maternal body size, and well provisioned with yolk. Eggs vary from about 0.02 to 20 mm in length. To prevent desiccation, they are covered by some of the most resistant and impenetrable egg coverings found in the animal kingdom. Egg contents are protected by a vitelline membrane and covered by an external hard shell, the chorion.