moth

A tropical moth larva in a Costa Rican rainforest. The larva is shown eating; this stage is the main nutritive stage of a moth's or a butterfly's life cycle. The larva will metamorphose into a pupa; during the pupal stage, the insect will rest for days, weeks, or even months, before emerging as an adult moth.

Any of a large number of mainly night-flying insects closely related to butterflies. Their wings are covered with microscopic scales. Most moths have a long sucking mouthpart (proboscis) for feeding on the nectar of flowers, but some have no functional mouthparts and rely instead upon stores of fat and other reserves built up during the caterpillar stage. At least 100,000 different species of moth are known. (Order Lepidoptera.)

Moths feed chiefly on nectar and other fluid matter; some, like the hawk moths, frequent flowers and feed while hovering. The females of some species (such as bagworm moths) have no wings at all or wings that are reduced to tiny flaps. Moths vary greatly in size: the minute Nepticulidae sometimes have a wingspread less than 3 mm/0.1 in, while the giant Noctuid or owlet moth (Erebus agrippina) measures about 280 mm/11 in across. In many cases the males are smaller and more brightly coloured than the females.

The larvae (caterpillars) have a well-developed head and three thoracic (middle) and ten abdominal (end) segments. Each thoracic segment has a pair of short legs, ending in single claws; a pair of suckerlike feet is present on segments three to six and ten of the end part of the body. In the family Geometridae the caterpillars have abdominal feet only on segments six and ten of the end part of the body. They move in a characteristic looping way and are known as ‘loopers’, ‘inchworms’, or geometers. Projecting from the middle of the lower lip of a caterpillar is a tiny tube or spinneret, through which silk is produced to make a cocoon within which the change to the pupa or chrysalis occurs. Silk glands are especially large in the silkworm moth. Many caterpillars, including the geometers, which are hunted by birds, are protected by their resemblance in both form and colour to their immediate surroundings. Others, which are distasteful to such enemies, are brightly coloured or densely hairy.

The feeding caterpillars of many moths cause damage: the codling moth, for example, attacks fruit trees; and several species of clothes moth eat natural fibres.

The corn earworm moth infests corn. The largest North American moths are the cecropia moth and polyphemus moth with wingspreads up to 14 cm/5.5 in.