BIOLOGY OF MOTHS

Moths are very similar to butterflies both in structure and life history, but on the whole they are nocturnal insects, whereas butterflies fly during the day. Another difference lies in the fact that the antenna? of butterflies are knobbed at the tips while those of moths are pointed. There are also slight differences in connection with the wings. When a moth is at rest its wings lie horizontally and are not folded vertically over the back as in a butterfly. The fore and hind wings of a butterfly are not connected, but those of a moth are locked together by means of a bristle at the base of each hind wing, which fits beneath a catch on the fore wing.

THE MAGPIE MOTH

The Magpie or Currant Moth is common during spring and summer and is sometimes mistaken for a butterfly because of its bright colour and the fact that it flies during the day. Its wings measure about 2 in. across, and have a creamy white background which is spotted and blotched with black. The front pair have also a yellow band running across the wing, and are marked with yellow at their bases. The body of the moth is yellow, marked with black.

The eggs are laid in May or June on currant or gooseberry leaves, often in such numbers that the resulting caterpillars become a serious pest. The caterpillar has a black head and a white body which is marked with black blotches and dots. The first three segments behind the head each bear a pair of jointed legs, but instead of the five pairs of pro-legs found in the caterpillar of the Cabbage White, there are only two, which occur on the 6th and last abdominal segments. Because it possesses only two pairs of pro-legs, the caterpillar does not crawl in the same way as the caterpillar of the Cabbage White. When crawling, the magpie larva first grasps with the thoracic legs, and then takes a fresh grip just behind these legs with the last pair of claspers, so that the body is bent in the form of a loop. Next the thoracic legs release their hold and gain a fresh grip after the body has straightened out. Because of this mode of travelling, the larvae of the Magpie moth and related moths are known as loopers, and the order to which these moths belong is named Geometrida?.

After becoming fully grown in June, the caterpillar crawls to some crack in a fence or in the bark of a tree, where it spins a silken covering called a cocoon and becomes a pupa. The head end of the pupa is rounded and the abdomen tapers to a point. The thorax is coloured black, while the abdomen is black with yellow rings. The moth passes the winter in the pupal stage and the imago emerges in the spring, but occasionally the emergence takes place before the winter, in September.

THE CLOTHES MOTH

This moth is a serious pest in houses. The small fawn-coloured female moths lay their eggs during the late summer and autumn months on woollen garments, blankets and carpets. The caterpillars which hatch out from the eggs in the spring feed on the wool before pupating in situ. The moths emerge and mate in August and September. Various methods of preventing damage by this insect are employed. The moths seek secluded places such as cupboards where woollen goods are stored and may be discouraged from laying their eggs in such places by the use of ’moth balls ’made of naphthalene or camphor, the vapours of which seem to be obnoxious to them. The best method, however, is the moth-proofing of woollen fabrics by impregnating them with D.D.T. or other suitable insecticides.

Practical Work on Butterflies and Moths

Examine the eggs, larva, pupa and imago of common butterflies and moths.

Scrape a few scales from the wing of a butterfly or moth on to a slide and examine under the microscope.

Examine the head of a butterfly or moth with a hand lens and make out the structure of the proboscis.

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