The caterpillar will spend much of its life in this bag, hanging from a branch. It is when they crawl around for food that people begin to notice them. The plant-covered cocoon is carried along with them and they move somewhat like turtles, pushing their heads out of the bag to advance forward. Once some ground is covered, they then drag their back ends to catch up. The result is what looks like strange genetics experiment: half worm, half plant.
Once the caterpillar's life stage is over though, it will pupate in the bag it created and emerge a dark and furry moth with feathery antennae. Wingless adult females will keep their bags. Males will fly to females to mate and females lay their fertilized eggs in their old bags. Once the larvae hatch, they will create their own silk bags of debris.
This species of moth is usually found in areas with conifer trees. Red cedar and arbor vitae are very popular choices and many bags are made of dried arbor vitae needles. The caterpillars are usually seen in the summer; adults usually in early autumn.