eastern tent caterpillar moth

Eastern tent caterpillar moth is a common, well known, medium-sized, lappet moth. It occurs in the United States and southern Canada east of the Great Plains, and there are scattered records in the west. It is very common in Minnesota.

The larvae feed on the leaves and buds of trees. Their preferred host by far is black cherry, followed by apple, chokecherry, American plum, and hawthorn. When their favorite trees are defoliated, late stage (instar) caterpillars may move to other, less desirable, deciduous trees. Final instar caterpillars are indiscriminate in their food choice, and they have been recorded feeding on a large number of species. Adults are short lived, lasting only a few days at most. They have non-functional mouth parts and they do not feed.

Eastern tent caterpillar moth is not considered a pest. A large infestation can completely defoliate a tree. However, the caterpillar is easily controlled in commercial black cherry orchards by the insecticides already used to control more serious pests, and its other hosts have little economic value.

Adults are ⅝″ to 15 ⁄16″ (15 to 24 mm) in length and have a ⅞″ to 1¾″ (22 to 44 mm) wingspan. Females are much larger than males. The body is stocky and extremely hairy. The wings are held tent-like over the body when at rest.

The forewings are rounded at the tip. The color is variable, ranging from light brown to “warm fawn brown” to dark chocolate brown. They tend to be darker and more brownish in the male, lighter and more yellowish on the female. They are crossed by two cream colored (pale), oblique, straight or slightly bowed lines: the antemedial line (AM line), between the basal and median areas; and the postmedial line (PM line), that separates the median area from the postmedial area. The median area, between the AM and PM lines, is sometimes paler than the rest of the wing. There are no other distinctive markings. The fringe is pale with one large and a few small dark patches.

The hindwings of both sexes are the same color as the forewings. They usually have no pale markings, but sometimes they are crossed by a single, diffuse, pale line.

The mature caterpillar is up to 2¼″ (57 cm) long. It is black and steel blue with orange and white markings and an apparently continuous creamy white stripe down the middle (middorsal). The body is covered with medium-length pale and orange hairs.

Eastern tent caterpillar is usually identified by the conspicuous, white, tent-like nest it creates in the crotch of two or three branches.

Total length: ⅝″ to 15 ⁄16″ (15 to 24 mm)

Wingspan: ⅞″ to 1¾″ (22 to 44 mm)

Anywhere the host species are found

One generation per year: Late June to early July

Adults are active at night and will come to lights. The wings are held tent-like over the body when at rest.

The larvae do not feed in the tent. They spin a strand of silk as they crawl to a neighboring branch, then use the strand to return to the tent after feeding.

The female lays a mass of usually 150 to 200 eggs, sometimes many more. The egg mass is usually laid on a twig, and it almost completely encircles the twig. Sometimes, an egg mass is laid about six inches above the ground on the trunk of a small tree, the diameter of which is no more than 1½″. The larvae develop fully, enter a period of decreased activity (diapause) for a few months, become inactive, and overwinter, all within the egg case.

The larvae emerge the following spring about the same time as new leaves appear on the host tree. They immediately begin feeding on leaves and buds, and soon build a tent-like nest. The tent is often built in the crotch formed by two or three substantial branches. After 4 to 8 weeks, depending on the temperature, final instar caterpillars construct a cocoon and pupate. Adults emerge about two weeks later.

Black cherry is the preferred host, followed by apple, chokecherry, American plum, and hawthorn. Final instars are indiscriminate, feeding on a large number of species.

Adults do not feed.

Sources

4, 7, 21, 24, 27, 29, 30, 71, 75, 82, 83.

Very common

Subfamily
Some sources, including Catalog of Life and iNaturalist.org, place the genus Malacosoma in the subfamily Malacosominae. Most sources, including BugGuide, ITIS, NCBI, and Butterflies and Moths of North America, place it in the subfamily Lasiocampinae.

Species epithet
The International Code of Zoological Nomenclature (ICZN) formally requires the species name (epithet), when interpreted as adjectival in derivation, to agree in grammatical gender with the genus name. Most lepidopterists stopped following that rule years ago. The justification for not following the rule is name stability in Linnaean nomenclature. Strong justifications for not following the rule, instead using the original spelling, were made in articles by Sommer in 2002 and Welter-Schultes in 2012. Welter-Schultes contended that “In such a situation it can only be recommended to maintain the names in the incorrect forms as they are, and not to change them.” Since before 2002, almost all major Lepidoptera databases and catalogs have followed this principle of original orthography.

Eastern tent caterpillar moth was originally described as Bombyx americana by Fabricius in 1793. The genus Bombyx was defined very broadly. In 1820, the genus Malacosoma was erected specifically for tent-making caterpillars. Following the move, the species epithet was changed to americanum in order to agree in neuter gender of the new genus name.

Authoritative sources are not in agreement about the correct species epithet of eastern tent caterpillar moth.

GBIF, Catalogue of Life, BugGuide, Moth Photographers Group, NatureServe, iNaturalist, and Minnesota Biodiversity Atlas use the name Malacosoma americana.

ITIS, NCBI, Discover Life, Butterflies and Moths of North America, and Wikipedia use the name Malacosoma americanum.

Caterpillar

Caterpillar

Nest

Eastern Tent Moth
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Luciearl
May 2024

Location: Cass County

Location: Penninton Co. MN

Location: Backus (Cass County)

2 large tents on pink Crabapple tree, caterpillars only

Location: Rush City, MN.

Infested our crab apple and plum trees within a day or two. Have never seen them before until today.