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Clearwing Moths, Family Sesiidae

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Most clearwing moths are bee or wasp mimics.

Most clearwing moths are bee or wasp mimics.

Gyorgy Csoka, Hungary Forest Research Institute, Bugwood.org

The clearwing moths (family Sesiidae) look like anything but moths. Many mimic bees or wasps quite convincingly. Though most insect enthusiasts appreciate them for their unusual and clever appearances, some clearwing moth larvae can be major plant pests, which makes them less beloved by gardeners and orchard growers.

Description:

In clearwing moths, the wings resemble window panes. One or both pairs of wings lack scales over part of their surface, so they appear transparent. Moths in this group have long, narrow fore wings and shorter, broader hind wings. The anal wing veins will be conspicuous in the hind wings, but reduced in the fore wings.

Many clearwing moths bear bright colors and markings similar to bees or wasps. Some even have tiny yellow-tipped tufts on their legs, to look like they are carrying pollen. This trickery, known as Batesian mimicry, is intended to fool predators into steering clear of them.

Clearwing moth larvae reach lengths of 1-1.5 inches just before pupation. The caterpillars aren't often seen, since they are borers that live inside their host plants. They are usually white or slightly blush with darker head capsules. Their dark brown pupal cases are sometimes found protruding from exit holes in the bark of the host trees.

Classification:

Kingdom – Animalia
Phylum – Arthropoda
Class – Insecta
Order – Lepidoptera
Family - Sesiidae

Diet:

Clearwing moth larvae are borers that feed within the stems, trunks, or roots of their host plants. Some, like the squash vine borer, can cause significant harm to the plant. As adults, clearwing moths do not feed.

Life Cycle:

Like all moths and butterflies, clearwing moths undergo complete metamorphosis. Mated females oviposit eggs on the host plant, usually on the trunk or stem. When the larvae emerge (in 1-4 weeks), they must bore their way into the host, where they feed and molt until ready to pupate.

Overwintering may occur in either the larval or pupal stages, depending on the species. Those clearwing moths that use woody plants as hosts may remain within the tree or shrub until warm weather returns, and then emerge as adults. Some species, especially those that inhabit plants that die back at the end of the growing season (like squash), typically overwinter in the soil as pupae.

Special Adaptations and Behaviors:

Clearwing moths fly during the day or at dusk, and they will even frequent flowers blossoms, completing the illusion that they are bees, and not moths.

Adult female moths emit strong sex pheromones to attract males. Synthetic pheromones can be used to attract and capture males of pest species like peach tree borers.

Range and Distribution:

Clearwing moths live throughout the world, except in the coldest habitats. The family Sesiidae includes over 1,100 species, with about 120 known from North America.

Sources:

  • Borror and DeLong's Introduction to the Study of Insects, 7th Edition, by Charles A. Triplehorn and Norman F. Johnson.
  • Clearwing Moths, Pest Notes, University of California, April 2004.
  • Family Sesiidae, Butterflies and Moths of North America website. Accessed January 14, 2013.
  • Family Sesiidae, North Dakota State University. Accessed January 14, 2013.
  • Sesiidae Specimens, San Diego Natural History Museum. Accessed January 14, 2013.
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