What are these?

Asked November 29, 2016, 8:52 PM EST

We are trying to identify these things hanging from outside door frames and walls, mostly along edges and in corners. Can you help?

Maui County Hawaii

1 Response

This is the cocoon of the grass bagworm caterpillar (larvae of the moth) (Brachycyttarus griseus). The common name "bagworm" is due to the bag-like silken case covered with pieces of grass in which the larva and adult female live. The larvae (caterpillar) chew on blades of grass while carrying their "bag". Ragged appearance of grass may be noticeable but the first evidence will most likely be the conical silken case with dead grass attached hanging from branches of shrubs, buildings, or other structures. Large numbers of bags are often noticeable. Adult female moths will remain in cocoon and attract male moths. Shortly after mating she lays several hundred eggs within the silken case and then dies. The eggs are deposited within the silken case. They hatch and the young larvae crawl out of the bag, construct their own conical silken case that is carried upright.
These are not huge pests and brushing the silken cases from structures may provide a measure of control.