# Fall webworm (Hyphantria cunea) > A widespread moth whose gregarious caterpillars build conspicuous silk webs on tree branches and feed on many deciduous trees. Source: https://insectscanner.com/species/fall-webworm/ (updated 2026-10-10) ## Is it dangerous? **Irritating hairs.** Caterpillar hairs can cause mild skin irritation or an itchy rash (contact dermatitis) in sensitive people if handled. Wash skin with soap and water and avoid rubbing. Eye exposure requires flushing with water and medical attention if irritation persists. **Pets:** Pets that groom or chew hairy caterpillars may develop oral irritation, vomiting or paw/face irritation; reactions are usually mild but seek veterinary advice if signs are severe. ## Quick facts - Scientific name: Hyphantria cunea - Also called: Fall webworm moth - Order: Lepidoptera (Moths and butterflies) - Family: Erebidae (Tiger moths and relatives) - Size: Wingspan 25-35 mm - Colours: White, Pale yellow, Brown, Black - Habitat: Edges of woods, parks, urban and suburban trees, orchards, hedgerows - Range: Native to North America (southern Canada to Mexico); introduced and established in central and southern Europe and in East Asia (Japan, Korea and China) - Active: One to several generations per year depending on region; caterpillars commonly in late summer and fall; adults nocturnal - Lifespan: Adults live about 1-2 weeks; entire generation from egg to adult about 6-8 weeks depending on temperature - Effect on plants: Defoliator - Pest: yes ## Overview Hyphantria cunea is a moth in the tiger moth family whose larvae (caterpillars) are well known for forming communal silk tents on the ends of deciduous tree branches. Native to North America, it has spread to parts of Europe and Asia. Caterpillars are generalist leaf feeders and occur in late summer and autumn in temperate areas. Although defoliation can be locally heavy, healthy trees usually recover after one season. Adults are white moths often seen at night and attracted to lights. Females lay masses of eggs on the undersides of leaves; the newly hatched larvae feed together and construct silky webs that protect them while they feed. Several color forms of larvae exist (pale to dark) and the species shows some variation in pheromones and behaviour across its range. ## How to identify it Adult moths are mostly white, wingspread about 25-35 mm, sometimes with small dark spots (more common in some populations). Caterpillars are densely hairy (setose) and vary from pale yellowish to dark brown or black with longitudinal stripes and a line of spots along the back; they carry tufts of longer hairs. Larval communal nests are conspicuous sheets of white silk that envelope foliage at branch tips. - Look for white silk webs (tents) enclosing foliage at branch tips in late summer and fall. - Caterpillars are densely hairy with variable coloration and a noticeable line of dorsal spots; they feed together inside the web. - Adults are plain white moths with a wingspan about 25-35 mm; some populations show small dark wing spots. ## Lookalikes - **Eastern tent caterpillar** (Malacosoma americanum): Eastern tent caterpillars build tents in branch forks in spring (not branch ends in late summer) and larvae have a distinct white dorsal stripe; they are in a different family (Lasiocampidae). - **Forest tent caterpillar** (Malacosoma disstria): Forest tent caterpillar lacks communal silken tents; larvae have keyhole-shaped dorsal spots rather than the dense hairy Hyphantria caterpillars. ## Life cycle - **Egg mass:** Females lay flattened masses of eggs on the undersides of leaves; eggs hatch in about 1-2 weeks depending on temperature. - **Larva (caterpillar):** Gregarious, hairy caterpillars feed communally and build silk tents around feeding sites. Larval stage lasts several weeks with multiple instars. - **Pupa:** Larvae pupate in loose cocoons in leaf litter, soil or bark crevices; pupation lasts 1-3 weeks in summer, and the last generation of the year overwinters as a pupa. - **Adult (moth):** Nocturnal white moths that mate and lay eggs; adults live about 1-2 weeks. ## Diet and predators - Young eat: Leaves of many deciduous trees and shrubs (generalist feeder) - Adults eat: Adults do not feed much; may drink nectar or not feed substantially - Predators of the young: Birds, predatory insects, parasitic wasps and flies that attack caterpillars or pupae - Predators of adults: Bats, night-flying insectivorous birds, and predatory insects ## Effect on plants and gardens Feeds on leaves of many deciduous trees and shrubs (over 100 host species documented), including apple, cherry, walnut, hickory, maples, poplar, willow and many ornamental species. Heavy localized defoliation can occur but healthy mature trees usually refoliate. ### How to get rid of it Prune and destroy small webs by hand or with pruning tools when nests are small; for larger infestations, targeted applications of Bacillus thuringiensis kurstaki (Btk) are effective against young caterpillars and are selective. Chemical insecticides can be used following label directions. Encourage natural enemies like birds and parasitic wasps. Always follow local regulations and safety instructions. ## Where and when to find it Find larval webs at the tips of branches on many deciduous trees and shrubs; search leaf undersides for egg masses in summer. Adults are attracted to porch lights at night. - Best time: Late summer to autumn for caterpillars; evenings and nights for adults. Check local phenology—some regions have earlier or later broods. - Tips: Photograph the communal silk tents and caterpillars from a safe distance to avoid skin contact. If collecting for study, wear gloves and place specimens in a sealed container. ## Fun facts - Despite the common name 'fall webworm', regional populations may have multiple generations per year and can be seen outside autumn in warmer areas. - The communal webs help protect caterpillars from some predators and allow group feeding on exposed leaves. - This species has spread widely outside its native range, partly through human movement of nursery stock and shipping. ## Frequently asked questions ### Are fall webworms dangerous? Only mildly. They are not venomous and do not bite or sting, but caterpillar hairs can cause mild skin irritation in sensitive people. ### Do fall webworms bite or sting? No. They do not bite or sting, but contact with their hairs can produce itching or a rash. ### Why are there webs on my tree? Those are communal silk tents made by fall webworm caterpillars to shelter themselves while feeding on the leaves at branch tips. ### Will fall webworms kill my trees? Usually not. Heavy defoliation can weaken young or stressed trees, but healthy mature trees typically refoliate and recover. ### How do I get rid of fall webworms? Remove and destroy small webs by pruning or snapping them open and exposing caterpillars to predators. For larger infestations, apply Bacillus thuringiensis kurstaki (Btk) to young caterpillars or use registered insecticides following label instructions. ### When are fall webworms most active? Caterpillars are most visible in late summer and fall in temperate regions; adults are nocturnal and attracted to lights. --- More about this species: [iNaturalist](https://www.inaturalist.org/taxa/127133), [Wikipedia](https://en.wikipedia.org/wiki/Fall_webworm). Identify insects and spiders from a photo with the Insect Scanner iPhone app: https://apps.apple.com/app/id1543946563?pt=126685406&ct=web-markdown&mt=8 Identification from photos is never certain: don't handle insects you can't identify, and get medical advice for bites, stings or allergic reactions.