Life cycle of the housefly:
The housefly undergoes complete metamorphosis. It exhibits all the four stages in its life history-egg, larva, pupa and adult. Metamorphosis may be defined as the reorganization of tissues and organs of a larva to transform it into the adult form. In complete metamorphosis, the life history stages include the larva and pupa that is different from the adult in structure and behavior.
Adult housefly:
The body of the adult housefly is divided into a distinct head, thorax and abdomen. The head has two compound eyes and a pair of small and sensitive antenna. The mouth parts include a tubular proboscis for sucking food. The thorax has 3 pairs of legs. Legs are hairy and have sharp claws and spines for the fly to cling to objects. The housefly has 1 pair of thin transparent wings.
The abdomen is segmented and soft. The housefly breeds on decaying organic matter including human and animal excreta.
Eggs:
The female lays about 100 eggs, each time for about 6-7 times during the breeding season (April - September). The eggs are white, cylindrical and 1 mm long.
Larva:
The egg hatches after 12 hours into a white coloured larva called maggot. The larva is the eating stage. The body of the larva is composed of twelve segments. The larva is long and conical with no legs. It locomotes with the help of the mouth and spiny pads located on the underside of the last seven segments. The larvae feed and grow in size by moulting. A fully-grown larva is about 2 cm.
Pupa:
The larva changes into the Pupa, the resting stage. The outer covering of the pupa is called the cocoon or puparium. The pupa is dark coloured and barrel shaped. Inside the puparium, the insect undergoes metamorphosis to form the fly. The pupal stage lasts for 5 days.
The housefly comes out by breaking the puparium. Once out of the puparium, the fly does not grow in size. In about 2 weeks, the fly is mature enough for reproduction.