The bagworm is distributed throughout the eastern half of the United
States. It is generally recognized as a defoliator of conifers,
particularly juniper, cedars, and arborvitae, but it is also found on
many hardwood trees including maple, wild cherry, poplars, oaks, and
apple.
[Illustration: Bagworm cases on pine.]
The wingless, maggot-like adult female bagworms are present in September
and October and spend their entire lives within the protective cover of
the tough, silken bag which they construct as larvae. Males are quite
agile fliers and can often be seen in the fall flying around infested
shrubs in search of a mate. Mating takes place through the open end of
the bag. Shortly thereafter the female deposits her egg mass containing
500 to 1,000 eggs in her pupal case. The eggs remain in the bag
throughout the winter. In the deep South, hatching can occur as early as
April, but occurs in May or June further north. During the early stage
of development, the larvae, housed in their tiny bags, are quite
inconspicuous. As they mature, the bags become quite noticeable, and the
amount of foliage consumed increases rapidly.
Outbreak populations of bagworm are in most cases quickly reduced by low
winter temperatures and a complex of several parasites. On shrubs and
shade trees around a home, it is often practical to control bagworms by
picking and destroying the bags.