Malacosoma constricta

Larvae distinguished from other western tent caterpillars by the combination of: orange dorsal hairs with grayish/cream lateral hairs, dark blue head, and speckled sides. The restriction to oak hosts in California, Oregon, and Washington provides geographic and ecological separation from M. californicum (western tent caterpillar), which occurs on diverse hosts including desert almond, cherry, apple, alder, poplar, and willow. M. americanum (eastern tent caterpillar) occurs east of the Rocky Mountains. The small tent size (up to 10 cm) and rudimentary structure contrasts with the larger, more elaborate tents of M. americanum.

Larvae have orange hairs on the dorsal surface, grayish or cream-colored hairs on the sides, and speckles along the lateral margins. The head is dark blue. Larvae spin silken tents up to 10 cm wide. Eggs are laid in golden yellow clumps along sticks. Adult moths are not described in available sources.

California oak woodlands and associated oak-dominated habitats. Larvae reported only on oaks (Quercus spp.).

Endemic to western North America: California, Oregon, and Washington. In California, subspecies M. c. austrinum ranges from Santa Barbara County southward; M. c. constrictum occurs from Los Angeles County northward.

Larval activity coincides with spring leaf flush of oaks. Specific adult flight period not documented in available sources.

Larvae feed on oak (Quercus spp.) leaves. Gregarious feeding behavior results in localized defoliation of branches.

• Quercus - primary hostOnly reported host genus; larvae feed on leaves

Eggs overwinter in golden yellow clumps laid along sticks. Larvae hatch in spring and construct silken tents. Larvae feed in groups outside the tent, entering only to molt. Pupation details not documented; likely occurs in silken cocoons away from host tree based on congeneric patterns. Adults emerge as moths; specific timing unknown.

Larvae exhibit communal living in silken tents. Group foraging outside the tent; tent used primarily for molting and thermoregulation. Trail-marking pheromones likely used for recruitment to food sources, as documented in congeners, but not explicitly confirmed for this species.

Defoliator of oaks; localized branch defoliation occurs but typically does not cause major damage to healthy trees. Serves as food source for predators and parasitoids. May contribute to nutrient cycling through frass deposition.

Occasional nuisance when present in high numbers. Aesthetic impacts from visible tents and defoliation. Control rarely necessary; manual removal of egg masses or tents effective. Not associated with Mare Reproductive Loss Syndrome (unlike M. americanum).

• Malacosoma californicumWestern tent caterpillar; broader host range (desert almond, cherry, apple, alder, poplar, willow), not restricted to oaks; occurs in desert and montane habitats beyond oak woodlands
• Malacosoma americanumEastern tent caterpillar; geographically separated (eastern North America), hosts on Rosaceae (cherry, apple, crab apple), constructs larger and more elaborate tents in branch crotches
• Malacosoma disstriaForest tent caterpillar; lacks true tent, makes silken mats on branches, broader host range including maple, birch, aspen

• tent caterpillar
• oak specialist
• gregarious
• defoliator
• western North America

• BugGuide
• Wikipedia
• GBIF taxonomy match
• iNaturalist taxon
• Catalogue of Life
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