Seasonal development and life cycle—Western tussock
Tussock moth eggs are laid in midsummer and do not hatch until the following spring; there is only one
generation a year except in Southern California where there are two. Eggs are
commonly deposited on branches and twigs in an egg sac, usually on an empty tussock moth pupal case.
pupal cases, which are easier to find than
the eggs themselves, are light brown,quite hairy,
and about 0.5 inch long. Look for them in the dormant season
on leafless trees. Eggs hatch when trees leaf out, causing
damage in spring. When they arefull grown, larvae spin their
emerge between late spring and midsummer. Adult males are winged; females are wingless and lay a single
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