Evergreen Bagworm Moths (Thyridopteryx ephemeraeformis)

Habits and Traits of Evergreen Bagworm Moths

If you are unfamiliar with bagworm, you might never notice it on the evergreens in your yard. Cleverly disguised in their bags made from the foliage of the host tree, Thyridopteryx ephemeraeformis larvae feed on cedars, arborvitae, junipers, and other favorite landscape trees.

Description

Despite its nickname, Thyridopteryx ephemeraeformis is not a worm, but a moth. The bagworm lives its entire life cycle inside the safety of its bag, which it constructs with silk and interwoven bits of foliage.

The larval form appears worm-like, hence the name bagworm.

Identifying bagworm in the landscape requires a good eye capable of recognizing their excellent camouflage. Because bagworm usually infests evergreen trees, the brown bags may be overlooked at first, appearing like seed cones. Look for suspicious cone-shaped bundles of dried brown foliage, up to 2 inches long, that match the tree's needles or leaves.

Only the adult male moth leaves the protection of its bag when ready to mate. The moth is black, with clear wings that span roughly an inch across.

Classification

Kingdom - Animalia

Phylum - Arthropoda

Class – Insecta

Order – Lepidoptera

Family - Psychidae

Genus - Thyridopteryx

Species - ephemeraeformis

Bagworm Diet

Bagworm larvae feed on the foliage of both evergreen and deciduous trees, especially these favorite host plants: cedar, arborvitae, juniper, and false cypress. In the absence of these preferred hosts, bagworm will eat the foliage of just about any tree: fir, spruce, pine, hemlock, sweetgum, sycamore, honey locust, and black locust.

Adult moths do not feed, living just long enough to mate.

Life Cycle

Bagworm, like all moths, undergoes complete metamorphosis with four stages.

Egg: In late summer and fall, the female lays up to 1,000 eggs in her case. She then leaves her bag and drops to the ground; the eggs overwinter.

Larva: In late spring, larvae hatch and disperse on silken threads.

They immediately begin feeding and constructing their own bags. As they grow, the larvae enlarge their bags by adding more foliage. They stay within the safety of their bags, sticking their heads out to feed and carrying the bags from branch to branch. Frass falls out of the bottom end of the cone-shaped bag through an opening.

Pupa: When the larvae reach maturity in late summer and prepare to pupate, they attach their bags to the underside of a branch. The bag is sealed shut, and the larvae turn head down inside the bag. The pupal stage lasts four weeks.

Adult: In September, adults emerge from their pupal cases. Males leave their bags to fly in search of mates. Females have no wings, legs, or mouthparts, and remain within their bags.

Special Adaptations and Defenses

The bagworm's best defense is its camouflage bag, worn throughout its life cycle. The bag allows otherwise vulnerable larvae to move freely from place to place.

Female moths, though confined to their bags, attract mates by releasing strong sex pheromones. Males leave their bags to find partners when they sense the chemical alert from females.

Habitat

Bagworm live anywhere suitable host plants are available, especially forests or landscapes with cedar, juniper, or arborvitae.

In the U.S., bagworms range from Massachusetts south to Florida, and west to Texas and Nebraska. This pest is native to North America.