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Snailcase Bagworm - Apterona helix   
Whitney Cranshaw, Colorado State
University, www.forestryimages.org
 HOSTS: Willow, mountain mahogany,
fruit trees, sage brush, rabbitbrush,
and various native and non-native cultivated plants. DESCRIPTION:
All
stages of this insect take place within a coiled, snail-like case that
looks like it is made out of dirt. Larvae are greenish or reddish-gray
caterpillars with a black head. Adults are wingless and nearly legless
moths; they mate while still within the case. LIFE
CYCLE: Larvae
become active in mid-spring and feed on leaves. As the larvae grow and
develop they produce a snail-like case out of silk and soil particles.
Larvae are mobile and carry the case upright. They mature in late
spring to early summer when they migrate to buildings, fence, and/or
trees to pupate. Transition to the adult moth takes place in the pupal
covering over several weeks. Eggs hatch in mid-summer and the larvae
remain in the pupal covering throughout the winter until becoming
active in the spring. CONTROLS:
Control is
very difficult since the insect is inside a protective case.
Fortunately, this pest does little damage in western Montana.Mechanical: Using a pressure-washer with soapy water will remove bagworms from buildings. Biological: If you catch larvae when they are feeding in the spring, Bt-kurstaki (for larvae of moths and butterflies) may reduce populations, though results have not been good in Missoula. |
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