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Plaster Bagworm (Phereoeca spp)

Facts, Identification & Control

The plaster bagworm is a species of moth. It requires high humidity to survive. Because of this, they are not commonly found inside air-conditioned buildings.

Where do they live?

They are quite common in garages, underneath buildings, on wool rugs and wool carpets, hanging on curtains, hanging from subflooring, joists, sills and foundations; on the exterior of buildings in shaded places, under farm sheds, under furniture, on stored farm machinery and on tree trunks. 

How do they live?

The plaster bagworm has 4 life stages: egg, larva, pupa and adult. After mating, females lay their eggs on crevices and the junction of walls and floors, cementing them on debris. 200 eggs may be laid by a single female over a period of a week, after which she dies. Eggs are soft, pale blue, and about 0.4 mm in diameter. The entire cycle from egg to adult averages 62-86 days.

The larvae of bagworms live in the characteristic gray, seed-shaped case, which measures about 13 mm long. The case is constructed of silken fiber and sand particles, lint, paint fragments, and other debris. The case has a slit-like opening at each end, and the tiny caterpillar is able to move around and feed from either end.

A fully developed bagworm caterpillar is about 7 mm long. It has a dark brown head, while the rest of the body is white.

Adult moths do not appear to feed. They fly fairly well, but usually rest on walls, floor edges, or on the webs of house spiders.

How do they affect us?

The larvae mainly feed on spider webs; however, they will also feed on fabrics made of certain natural fibers like wool. Clothes closets should be checked regularly to ascertain integrity of woollen items therein. Certain species such as the Evergreen bagworm feed on the upper parts of plants leaving holes in the foliage. In large populations they can make life very difficult for orange farmers and producers.

How do we control them?

Regular cleaning practices can reduce the incidence of the plaster bagworm. Outdoors, manual picking of cases when the populations are relatively low should be enough to keep this species under control.