All About Bagworms
Bagworms have a fascinating life cycle! After hatching, each caterpillar spins a silk and leaf “bag” around itself. These bags are protective against predators, and are easily carried by the caterpillar as it crawls around feeding on trees and shrubs. If you see one of these little bags moving, look closely and you will see the head and front legs peeking out of the front of the bag.
The caterpillars feed and grow throughout the summer, then pupate in August or September. The male emerges as a moth, and seeks out a female, which remains inside the bag her entire life. The male is able to breed her inside the bag via a long appendage. She will lay her eggs inside the bag, and then die. When the eggs hatch the next spring, the tiny larvae lower themselves by silk strands and float to other trees and shrubs to begin feeding and building their own bag and complete their life cycle.
If you find a few of these little critters on your shrubs or trees, simply pick them off and dispose of them. They rarely do much damage. But, if plentiful, spray with Bt, Spinosad, Neem oil or Insecticidal soap in the spring just after the eggs have hatched. Chemical control is not as effective once the caterpillars close up their bag to pupate in late summer.