western tent caterpillar has one generation a year and over winter
in the egg stage. In early spring, when deciduous trees begin
to leaf out, larvae hatch from the eggs and feed on the emerging
leaves. Western tent caterpillars find safety in numbers; the
larvae aggregate together in communal silken tents during the
night. Tents are usually formed in the crotches of smaller branches.
Young larvae do not venture far from the tent and usually feed
on the foliage of a single branch.
hatched egg mass
on newly constructed tent on apple
Western tent caterpillar’s (Malacosoma californicum
pluviale) body is dark with spots of white, orange and blue.
White and orange-yellow tufts of hair poke out from each segment.
Forest caterpillar is blue with spots of black, white and orange.
The markings along the back resemble shoe-prints
As larvae mature,
the caterpillars begin to become more solitary, feeding by themselves
or in smaller groups. In June, the mature larvae wander away from
the host tree and pupate by forming a white, puffy cocoon. After
about ten days, adult moths emerge from the cocoon. Shortly after
emerging, the adults mate. Adult moths are hairy, reddish-brown,
stout moths. Often you will find these moths head-butting your porch
light bulbs in June and July. Females seek new host trees to lay
eggs on. Eggs are laid in frothy masses in batches of 100 to 350
on host tree branches. The eggs will stay glued on the tree until
the larvae hatch next spring.
congregated on tent.
in tall grass to pupate into adult moths.