Fall webworm vs Forest tent caterpillar moth
These two are easy to mix up. Here's how to tell a fall webworm from a forest tent caterpillar moth, and whether either one bites or stings.
Fall webworm
Hyphantria cunea
Forest tent caterpillar moth
Malacosoma disstria
≠The key differences
Forest tent caterpillar lacks communal silken tents; larvae have keyhole-shaped dorsal spots rather than the dense hairy Hyphantria caterpillars.
Fall webworm creates loose silken webs around foliage late in summer and larvae are pale and hairy, lacking the dark body with keyhole dorsal spots of forest tent caterpillar.
⚖︎Side by side
| Fall webworm | Forest tent caterpillar moth | |
|---|---|---|
| To humans | Irritating hairs | Irritating hairs |
| Size | Wingspan 25-35 mm | 25-45 mm wingspan |
| Colours | White, Pale yellow, Brown, Black | Brown, Pale cream, Black, Blue-grey |
| Family | Erebidae | Lasiocampidae |
| Habitat | Edges of woods, parks, urban and suburban trees, orchards, hedgerows | Deciduous forests, mixed woodlands, urban trees and orchards where host trees occur |
| 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) | Widespread across much of North America, from Canada through the United States; range varies regionally with host availability |
| Active | One to several generations per year depending on region; caterpillars commonly in late summer and fall; adults nocturnal | Larvae active in spring and early summer (varies by latitude); adults on the wing in late spring to early summer, mostly dusk and night |
| Pest? | Yes | Yes |
🔍How to spot a fall webworm
- 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.
🔍How to spot a forest tent caterpillar moth
- Caterpillars have a row of pale, elongated keyhole- or footprint-shaped dorsal spots on a dark body — distinctive for this species.
- Unlike eastern tent caterpillar (Malacosoma americanum), forest tent caterpillar larvae do not build permanent silk tents in branches; they make ground or trunk mats.
- Adults are small brown moths with faint darker lines and a paler median band on the forewings; identification to species is easiest by larval characters.
?Frequently asked questions
What is the difference between a fall webworm and a forest tent caterpillar moth?
Forest tent caterpillar lacks communal silken tents; larvae have keyhole-shaped dorsal spots rather than the dense hairy Hyphantria caterpillars. Fall webworm creates loose silken webs around foliage late in summer and larvae are pale and hairy, lacking the dark body with keyhole dorsal spots of forest tent caterpillar.
Is a fall webworm or a forest tent caterpillar moth more dangerous?
Fall webworm: Irritating hairs. Forest tent caterpillar moth: Irritating hairs. Caterpillar hairs can cause mild skin irritation or an itchy rash (contact dermatitis) in sensitive people if handled. Adults are harmless.
Identification from photos is never certain: don't handle insects you can't identify, and get medical advice for bites, stings or allergic reactions.