Identify Moth Larvae: Clothes Moths to Hornworms

A moth larva is a caterpillar: it has three pairs of small jointed legs behind the head and fleshy prolegs on no more than five abdominal segments (UC IPM). Three look-alikes are worth ruling out:

• Sawfly larvae have prolegs on six or more abdominal segments (UC IPM) and often curl into an S shape (iNaturalist forum).
• Fly maggots have no true legs and often no visible head (UC IPM; University of Kentucky).
• Carpet beetle larvae, the other fabric pest, are hairy, leave brown bristly cast skins and make no webbing (UC IPM).

There are about 160,000 moth species, roughly 90 percent of the order Lepidoptera; butterflies are the rest (Wikipedia). So a caterpillar you cannot name is, on the odds, most likely a moth larva. For a general larvae key, see identify larvae.

Only a few moths have larvae that live indoors, and Wikipedia's moth article stresses that it is the larvae, not adult moths, that eat natural fibres. The two groups to know:

• **Webbing clothes moth (*Tineola bisselliella*):** larvae shiny white with a dark head capsule (UC IPM), up to 13 mm (Natural History Museum, London). They spin silk feeding tubes on the fabric.
• **Casemaking clothes moth (*Tinea pellionella*):** similar, up to 12 mm, but carries a silken case as it feeds (UC IPM; NHM). NHM notes a small difference visible under magnification: the common clothes moth larva has no simple eyes (ocelli), the case-bearing one has one.
• Where to look: under collars and cuffs, in crevices of upholstered furniture and in carpet under furniture (UC IPM). Adults are only about 1/4 inch at rest.
• Indianmeal moth: the pantry moth. Larvae grow to about 1/2 inch, greenish or pinkish, and leave silk threads wherever they crawl; mature larvae may wander far from the food to pupate (UC IPM).

For adult moths and other indoor moth look-alikes, see moth identification.

Outdoors there are thousands of moth caterpillars (the Wildlife Trusts note thousands of moth species in the UK alone), but three body types narrow them quickly:

• Inchworms, loopers and spanworms (Geometridae): only two or three pairs of prolegs, all at the rear, so they move by looping. They are often green, grey or brown, about 1 inch long, and many stand stiff to look like a twig (Wikipedia). The family has around 23,000 species, over 1,400 of them in North America.
• Hornworms (Sphingidae, hawk moths): medium to large, stout caterpillars with a horn at the rear end, which may shrink to a button in the last stage. The tobacco and tomato hornworms are the best known (Wikipedia). The Wildlife Trusts describe the elephant hawk-moth caterpillar, up to 8.5 cm, with eyespots at the front and a spiky tail.
• Hairy caterpillars: the Wildlife Trusts warn that the hairs of some, such as yellow-tail and brown-tail moth caterpillars, can irritate skin. Do not handle hairy caterpillars with bare hands; see woolly bear caterpillar.

For naming a caterpillar to species, photo galleries built by rearing larvae to adults are the most reliable references: Prairie Haven covers more than 200 species from Wisconsin, arranged by family, and NatureSpot's Leicestershire and Rutland gallery marks each species by how easy it is to identify.

Temperature, applied to the item, is what both UC IPM and the Natural History Museum describe:

• Freezing: several days in a freezer below 18°F (UC IPM); NHM gives -20°C for a week.
• Heat: at least 30 minutes above 120°F (UC IPM); NHM gives 49°C for over 30 minutes.
• Washing or dry cleaning: laundering at 120°F for 20 to 30 minutes, or dry cleaning (UC IPM).
• Vacuuming carpets and under furniture (UC IPM; NHM).
• Pheromone traps attract male moths and are mainly for detection (UC IPM; NHM).

For Indianmeal moths in food, UC IPM's first step is to throw away any food showing signs of infestation. Any insecticide must be one labelled for the use, applied as the label says.

There is no single month, because it depends on the species and on whether they live indoors. Indoors, clothes moths breed whenever it is warm enough: UC IPM says females lay an average of 40 to 50 eggs over 2 to 3 weeks, hatching in 4 to 10 days in warm weather, and NHM adds up to three weeks in colder weather. Outdoors, adults generally lay eggs on or near the plants their caterpillars will eat; the larval stage usually lasts four to eight weeks, but species that pause development over winter can take ten months or longer (Wikipedia, Moth).

Photograph the larva from the side so every pair of legs is visible, then from above. Include the plant or fabric it was on, since that is often the fastest clue. InsectLens identifies moth larvae and adults from photos.

Research and drafting for this page used AI assistance. Every figure, date and quotation was then checked line by line against the sources listed at the bottom of the page, each of which was opened while writing. Nothing here is a diagnosis. If a bite, sting or contact with an insect is followed by trouble breathing, swelling of the face or throat, spreading redness, fever or any symptom that worries you, get medical care; in the United States Poison Help (1-800-222-1222) is free and open 24 hours a day.