Moths are distinguished from butterflies by having threadlike or feathery antennae. Most are nocturnal. They vary in size from adults of some leaf miners with wings spreading little more than 3 mm to the Asian atlas moth, spreading 20 cm. The related cecropia moth, spreading 12 cm, is Canada's largest. Most moths have mouth parts modified into a coiled proboscis (tongue) for extracting nectar from blossoms.
Reproduction and Development
Moths undergo complete metamorphosis and have 4 developmental stages: egg, larva, pupa and adult. In many species, larvae live in shelters formed by rolling and tying leaves together (leaf rollers); others build portable cases in which to live (bagworms). Pupae are usually contained in a cocoon, or in a cell in the soil. Although most moth larvae are solitary, some live in colonies (webworms and tent caterpillars).
Moth larvae, called caterpillars, are usually plant feeders. Most consume leaves; others feed on roots (eg, ghost moth larvae), bore into tree trunks (carpenter worms), feed beneath the surface of leaves, stems or bark, thus forming tunnels (leaf, stem or bark miners), or bore into fruits or seeds (codling moth larvae). Some tropical moths and caterpillars are predators of flies.
The American tent caterpillar is a periodic pest in fruit-growing areas of eastern Canada. Larvae spin a silken nest in which they congregate when not feeding. Forest tent caterpillars, which feed on broad-leafed trees, do not form an actual nest, but gather in a mass in crotches of tree branches. In some years, forest tent caterpillars are numerous enough to damage large tracts of broad-leafed trees.
Interaction with Humans
One family (Sphingidae) of large moths attracts popular interest. It includes hawk or sphinx moths, distinguished by long, narrow wings and rapid flight. Although primarily nocturnal, they often fly at dusk and greatly resemble hummingbirds as they hover, feeding on nectar. Larvae of 2 species, tobacco and tomato hornworms, are occasional crop pests.
Another family (Tortricidae) of much smaller moths includes economically important species. The codling moth, a pest of apples, bores into fruit, making it inedible. Spruce budworm, the primary pest of Canada's forest industry, sometimes destroys vast acreages of conifers.
One of the largest families (Noctuidae) includes the owlet moths (millers) and many economically important larvae (cutworms). Cutworms hide in the surface layer of soil in daytime and feed on young plants at night, often severing stems at the surface. Several pest species occur in Canada, pale western, red-backed and black cutworms being among the most important.
The armyworm, another chronic pest, derives its name from larvae that march en masse from one stand of grain to another. Another group of Noctuidae contains species that bore into flowers and fruits (corn earworm, tobacco budworm).
Larvae of another large family (Geometridae) are called geometers or inchworms because of their unique means of locomotion. This family includes pest species responsible for defoliation of trees (spring and fall cankerworms). Clothes moths, which occur worldwide, are carried from house to house on clothing or other articles of animal origin. Their natural food is hair, wool and feathers.