American giant millipede vs Pill millipede

These two are easy to mix up. Here's how to tell an American giant millipede from a pill millipede, and whether either one bites or stings.

≠The key differences

Pill millipedes are shorter, more dome-shaped and can roll into a compact ball, whereas Narceus americanus is elongated and coils into a spiral.

	American giant millipede	Pill millipede
To humans	Irritating secretion	Non-toxic
Size	5-10 cm (50-100 mm) long	7-20 mm long (typical adult length)
Colours	Dark brown, Reddish brown, Cream, Black	Dark brown / black, Reddish brown, Pale yellow margin
Family	Spirobolidae	Glomeridae
Habitat	Moist terrestrial habitats: leaf litter, rotting logs, under stones, compost piles, and garden mulch; also inside basements and crawl spaces when moist	Leaf litter, under logs and stones, mossy banks, gardens, hedgerows and woodland in temperate regions; prefers moist microhabitats.
Range	Eastern and central North America, from the northeastern United States through the southeastern states; reports extend into parts of the Midwest and southern Canada	Widespread across western and central Europe and into parts of southern and eastern Europe; commonly recorded in the British Isles and mainland Europe.
Active	Mostly nocturnal and active in warm, wet seasons; activity peaks in spring through fall in temperate regions	Active mainly in damp conditions year-round in mild climates; most active spring to autumn and at night or during damp daylight hours.
Pest?	No	No

Large cylindrical body with many segments, each segment bearing two pairs of legs
Often 5-10 cm long and coils into a tight spiral when disturbed
Alternating darker dorsal coloration with lighter margins or subtle banding on segments
Short bead-like antennae and numerous short legs visible from the sides

Small, dome-shaped body that rolls into a tight ball (volvation) when disturbed.
Glossy dark dorsal plates, each with a pale whitish or yellowish rear edge.
Short, compact appearance with legs mostly hidden under the body when viewed from above.
Size typically 7-20 mm; adults have a smooth, rounded outline rather than elongate cylindrical shape.

Pill millipedes are shorter, more dome-shaped and can roll into a compact ball, whereas Narceus americanus is elongated and coils into a spiral.

American giant millipede: Irritating secretion. Pill millipede: Non-toxic. Not venomous or aggressive. Not dangerous.

Identification from photos is never certain: don't handle insects you can't identify, and get medical advice for bites, stings or allergic reactions.