How to identify insects and invertebrates under logs and stones

Use our ID guide by naturalist Brett Westwood to identify insects and invertebrates living under logs and stones.

Pill woodlouse. © Konrad Wothe/Getty

A variety of insects and other invertebrates take refuge under logs and stones, safe from large predators, or damaging frosts in winter. Turn over a log briefly, or peep under the flaps of peeling bark, and you’ll reveal a menagerie.

Advertisement

Logs and stones provide a safe refuge in winter, where temperatures are fairly stable – only in very cold weather will ice form underneath logs. In their winter torpor, large ground beetles don’t feed; instead, they will snuggle up to slugs and earthworms without attacking.

Similarly, you’ll sometimes see mollusc-munching carrion beetles alongside snails and pearly slug’s eggs. If you’re lucky you’ll spot the buzzing snail-hunter, with a long, narrow snout adapted to probe the recesses of snail shells and extract the soft bodies.

To avoid their attentions, many snails will be sealed safely behind a door of hardened mucus. In a mild spell slugs may emerge to graze, but when frosts bite most take cover, along with millipedes and woodlice, snug in their deadwood dormitory.

All illustrations by Felicity Rose Cole


How to identify insects and invertebrates under logs and stones

Violet ground beetle (Carabus violaceus, above)

Violet ground beetle. Felicity Rose Cole

20–30mm. Large beetle with purple wingcase borders. Feeds on worms and other soft-bodied invertebrates.

Woodlouse spider (Dysdera crocata)

Woodlouse spider. Felicity Rose Cole

9–15mm long. Found most frequently in southern England. Its huge orange jaws pierce woodlouse armour.

Buzzing snail-hunter (Cychrus caraboides)

Buzzing snail hunter beetle. Felicity Rose Cole

15–20mm. Long ‘snout’ probes snail shells. Also eats wide range of soft-bodied prey. Buzzes when handled.

Ground beetle (Abax parallelepipedus)

Ground beetle. Felicity Rose Cole

17–22mm. Black beetle with grooved wingcases. Eats earthworms and other soft-bodied invertebrates.

Carrion beetle (Silpha atrata)

Carrion beetle. Felicity Rose Cole

10–15mm. Mat-black beetle with broad wingcases. Feeds on snails and a wide variety of carrion.

Devil’s coach-horse (Ocypus olens)

Devil's coach horse beetle. Felicity Rose Cole

20–30mm. Black rove beetle with short wingcases. Raises tail when threatened. Eats slugs.

Common black millipede (Tachypodoiulus niger)

Common black millipede. Felicity Rose Cole

Up to 30mm. Coils when disturbed. Body has 30–60 segments. Feeds on decaying matter and fungi.

Flat-backed millipede (Polydesmus angustus)

Flat-backed millipede. Felicity Rose Cole

Up to 25mm. Brownish, winged segments; appears flatter than black millipede. Often found under bark.

Common pill woodlouse (Armadillidium vulgare)

Common pill woodlouse. Felicity Rose Cole

Up to 18mm. Found especially on limy soils. Similar pill millipede has more than seven pairs of legs.

Common striped woodlouse (Philoscia muscorum)

Common striped woodlouse. Felicity Rose Cole

Up to 11mm. Fast-moving. Grey, brown or even orange, often with dark stripe.

Garlic snail (Oxychilus alliarius)

Garlic snail. Felicity Rose Cole

6–8mm. Translucent, shiny, pale-brown shell, dark grey body. Emits strong garlic smell when disturbed.

Great grey slug (Limax maximus)

Great grey slug. Felicity Rose Cole
Advertisement

Very large slug, up to 20cm. Body dark grey, with paler blotches and stripes – hence alternative name of leopard slug.