Plume moths are unusual as they have wings split into distinct lobes or plumes and look superficially like tiny feathers. They are delicate creatures, and as they fly by night, they are only seen if disturbed from their daytime resting place.
There are about 1,000 species of plume moth worldwide. They all belong to the family Pterophoridae or Alucitidae (Many-plumed moths.) The Many-plumed moth differs from the others in having its wings divided into 24 plumes, while all the other plume moths have each forewing divided into two plumes and each hind wing into three.
Plume moths are rather small, with long, slender bodies and large, conspicuous legs bearing sharp spurs. At first sight, they do not look like moths at all, resembling small craneflies, particularly when in flight. Few of the species have distinctive markings, and they are not easy to identify.
The moths fly at night and are readily attracted to bright lights. During the day, they may be disturbed from where they rest. and after a short flight to escape the disturbance. they settle on a leaf, fence, or tree trunk.
The caterpillars feed on leaves, flowers, or within stems, depending on the species, and each tends to be restricted to a single species of food plant or a group of related plants.
One caterpillar, that of the marsh plume, feeds on sundew, an insectivorous plant, but seems to thrive despite the inherent danger of living on such a plant.
Many Plume Moth
Several species of plume moth occur in gardens, among them the many plume, a tiny moth that has 24 plumes of its wings. In the past, it was presumably a woodland species, as the caterpillars eat nothing but honeysuckle, a plant once confined to woods. As honeysuckle is now common in gardens, the moth appears there too. It is found throughout Britain and is abundant in many localities.
The caterpillar is pink, with a dark-spotted, pale brown head. It is found among the flower buds and flowers of honeysuckle, where it feeds chiefly on pollen, an unusual food for moth caterpillars. When fully fed, it pupates on the ground beside the food plant, first constructing a cocoon within which it is well hidden.
The moths hatch from the pupae in summer, then hibernate, only appearing with the first warm weather in the spring. They are sometimes attracted to lights on mild nights in winter but can often be found sitting motionless in a secluded spot in sheds and greenhouses or crevices on fences and walls.
The best way to see the moths is by gently tapping honeysuckle bushes in August and September. Any moths disturbed will emerge and fly a short distance, settling on nearby leaves.
Large White Plume
The large white plume is easily recognised by its larger size and brilliant white coloration. It is common and can be seen flying from June to July.
The female lays her eggs on bindweed leaves, often in hedgerows. When the caterpillars hatch, they feed for a short time but hibernate while still small. Bindweed dies during the winter, and the caterpillars start feeding again in spring when the first new leaves appear above the ground.
The caterpillars are bright green with yellowish stripes and are covered with tufts of whitish hair. When fully fed, they form pupae that resemble the caterpillars but cannot feed. They are immobile unless provoked when they jerk their thorax.
With its pale brown wings, legs, body, and forewings with a dark spot in the middle, the garden-dwelling Ochreous plume resembles several other plume moths which also inhabit gardens. The ochreous plume is fairly common around wasteland as well as gardens.
It flies during the night in August, and although it can be disturbed from vegetation during the day, it is much more likely to remain still and escape detection.
The female moth lays her eggs on the flower heads of tansy, a common plant of wasteland and gardens. After hatching, the young caterpillar bores a mine down into a flower stem to hibernate in the root.
Feeding recommences in spring when the caterpillar continues to mine, eating the internal tissues of the stem and sometimes causing it to wilt. When fully fed, the small, brown caterpillar leaves the mine and comes out into the open, forming a pupa attached to the stem.
The caterpillars of the triangle plume also mine into the stems of their food plant and the leaves and flowers. The female lays her eggs on the leaves and stems of coltsfoot. The caterpillars, whitish with black dots, hatch in September and at first mine into leaves, then later into the stems, where they hibernate. In spring, they burrow into buds and flower heads, eventually pupating in the seed head.
There are two broods each year, and caterpillars resulting from the first brood mine into leaves in June and July when coltsfoot is not in flower. The pupae of this brood are therefore formed inside silken cocoons on the underside of leaves.
The moth resembles the ochreous plume, but the dark spot on the forewing is usually triangular. The first brood flies at night in May and June, and the second in August and September.
Brown Wood Plume
This is similar in appearance to the two species described above but lacks the dark spot on the forewing. It is common in gardens, hedgerows, and woodland edges, providing a plentiful supply of its food plant, germander speedwell.
The female lays her eggs on the underside of the plant’s leaves. After hatching, the caterpillar bores into the stem and hibernates in a hole it makes low down in the stem, first constructing a protective cocoon.
In spring, it leaves the cocoon and climbs the plant to feed on the bright blue flowers. As its color resembles the flower, it is not easy to see.
Restricted to One Food Plant
The caterpillars of most species of plume moth are restricted to just one species of food plant, and the same is true of many other plant-feeding insects.
Virtually all plants produce some chemical substances in their leaves that play no part in normal growth and development but act as deterrents to insect attack. Thousands of different types of these chemicals are known.
During evolution, insects have developed the ability to overcome the toxicity of certain of these chemicals so that they can feed on a particular plant without adverse effects, hence the often narrow range of food plants to which many species are restricted.
The distinctive flavors of many of our foods and beverages are caused by the presence of such chemicals, and some insecticides are made from these naturally occurring defensive substances.