Bag Moth Cocoon

The caterpillar larvae of the Psychidae construct cases out of silk and environmental materials such as sand, soil, lichen, or plant materials. These cases are attached to rocks, trees or fences while resting.

Bagworm cases range in size from less than 1 cm to 15 cm among some tropical species. The attachment substance used to affix the bag to host plant, or structure, can be very strong, and in some case require a great deal of force to remove given the relative size and weight of the actual “bag” structure itself.

Adult females of many bagworm species have only vestigial wings, legs, and mouthparts. The adult males of most species are strong fliers with well-developed wings and feathery antennae but survive only long enough to reproduce due to underdeveloped mouthparts that prevent them from feeding.

Since bagworm cases are composed of silk and the materials from their habitat, they are naturally camouflaged from predators. Predators include

birds and other insects. Birds often eat the egg-laden bodies of female bagworms after they have died. Since the eggs are very hard-shelled, they can pass through the bird’s digestive system unharmed, promoting the spread of the species over wide area.

A bagworm begins to build its case as soon as it hatches. Once the case is built, only adult males ever leave the case, never to return, when they take flight to find a mate. Bagworms add material to the front of the case as they grow, excreting waste materials through the opening in the back of the case. When satiated with leaves, a bagworm caterpillar secures its case and pupates. The adult female, which is wingless, either emerges from the case long enough for breeding, or remains in the case while the male extends his abdomen into the female’s case to breed. Females lay their eggs in their case and die.