Snailcase bagworm

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Snailcase Bagworm
Conservation status
Secure
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Lepidoptera
Family: Psychidae
Genus: Thyridopteryx
Species: T. ephemeraeformis
Binomial name
Thyridopteryx ephemeraeformis
(Haworth, 1803)

The Snailcase bagworm (Thyridopteryx ephemeraeformis) is a caterpillar that looks like a small snail and never becomes a moth. It transforms into a wormlike adult in the late summer. Unlike most bagworms, the case is constructed of soil particles instead of leaves and twigs. The snailcase bagworm begins constructing its case at birth and remains inside for the rest of its life.

The case of a snailcase bagworm, not surprisingly, resembles a small snail about 4 mm in diameter with coloration similar to the soil. The larvae are greenish or reddish gray with a black head that protrudes from the case to feed.

These bagworms are native to Europe, but are now found in North America as well, where they are spreading. Only females have been collected in North America.

Snailcase bagworms feed on a variety of plant species. The creatures progressively gouge out small areas of a leaf surface, rarely causing significant damage.

When entering the pupa stage in the late spring to early summer, it sticks itself to a surface, causing some homeowners to complain about the crud sticking to the siding of their homes, not realizing that each small piece is a case for a snailcase bagworm. They seek out high, shaded areas to pupate. This species of bagworm can reproduce by parthenogenesis, without mating, though there are males and females. Each female produces one to two dozen eggs.

Though the snailcase bagworm doesn't cause the damage of related species such as the evergreen bagworm, they are a nuisance to humans by attaching to the sides of homes and buildings. Once the larvae are full-grown and moving to pupate, they cannot be controlled with insecticides. The best way to keep them off the sides of buildings is by using temporary barriers like sticky tape or flanges. They can be knocked off buildings with a strong spray of water before they attach. After they are attached, removal is difficult.