Isoptera

Order

ISOPTERA
(Greek, isos = equal; pteron = wing)

Description

There are about 2,300 species of these soft-bodied, social insects worldwide. Antennae are usually well developed and composed of very short, bead-like segments (moniliform). Mandibles are always well developed. Compound eyes may be present but are frequently reduced. Termites have a series of castes: workers, soldiers, queens and kings. Soldiers form two main groups: those with well developed mandibles for defence against enemies and those with a pronounced "snout" (nasus) through which sticky defensive secretions are ejected at the enemy. Wings are only present in reproductive castes and only for a short period. Wings are elongate, membranous and held flat over the body at rest. The wings have lines of weakness at their bases and are shed after dispersal from the termite mound. Many termite species consume wood or plant material but by themselves are incapable of cellulose digestion. Their gut flora contains symbiotic protozoans which are able to break down the cellulose and enable the termites to benefit from their diet. Without the social behaviour of these insects which involves food exchange between individuals, inoculation of the symbionts into newly hatched or moulted individuals would not occur.

Life Cycle

No metamorphosis occurs (e.g. egg-larva-pupa-adult); the newly hatched individual is a wingless nymph and may develop into any caste required by the colony.

Distribution

Cosmopolitan, mostly tropical and subtropical

Members

Termites or white ants.

Food

Wood or plant material of any kind including grass stems, old weathered dung pats or plant litter. Cellulose is digested by symbiotic protozoans in the termite gut. Some termite species cultivate fungi on the stored cellulose and feed on the fruiting bodies produced.

Importance

The destructive effects of termites on buildings is well known. Huge sums of money are expended annually to prevent termite infestations or to repair the damage done by these insects if they have invaded homes or other structures. Damage in tropical areas is especially severe unless care is taken with building design. Extremely toxic chemicals such as chlordane or lindane have been used in the past to combat termites but these substances are now banned from general use as they are extremely persistent in the environment. Tropical species of Australian eucalypts actually benefit from termite infestation. Once the dead heartwood is removed by the termite colony, the living sapwood forms a rigid cylinder which remains quite strong, enough to support the weight of the tree. The resulting hollow is often used by various animals whose droppings provide quantities of fertilizer for the tree for many years.