Growth and Development in Insects
Insects undergo metamorphosis.
Metamorphosis is complete or marked change in the form of an animal as it develops into an adult.
Insects lay eggs, which later hatch into larvae.
Larva is an immature stage, usually behaviourally and structurally different from the adult.
The larva is referred to as a grub, a maggot or a caterpillar depending on the insect.
The larva eats a lot, grows rapidly and sheds its cuticle several times until it reaches full size to become a pupa.
The pupa is an inactive, non-feeding stage during which during which extensive breakdown and re-organisation of body tissue occur, eventually giving rise to the imago or adult form.
(a) Complete Metamorphosis
The insects go through egg-larva-pupa-adult e.g. housefly.
Development in a Housefly
When egg of a housefly is laid, it hatches into larva. The larva grows and feeds decaying matter. After several moults and increase in size the larva changes into pupa encased in a pupal case called puparium. This later develops into an adult fly. After emergence the adult takes about two weeks of feeding and growing to attain sexual maturity i.e. the males can mate and the females able to lay eggs.
(b) Incomplete Metamorphosis
The insects go through egg-nymph-adult e.g. cockroach, locust
Development in a cockroach
Cockroaches lay eggs enclosed in a case called ootheca which is made up chitin. The ootheca is usually deposited in moist dark and warm places. After about a month, small wingless nymphs emerge. The nymphs feed, and moults about 10 times within about 16 days before changing into an adult cockroach.