Garden wildlife identifier: caterpillars

When fully grown, most moth caterpillars descend to the ground and burrow into loose soil to spin a silk cocoon for the chrysalis, in which the earth-bound maggot magically transforms into an aerial adult. Butterfly caterpillars tend to make their chrysalis on or near their food plant.

How to identify caterpillars

When finding caterpillars, the biggest clue to identifying them is to take note of where you found them. Many have specific host (food) plants and so if you find a caterpillar on a leaf you will be able to narrow down its identity by looking up caterpillars that feed on that type of leaf. For example, caterpillars found on nettles could be the larvae of small tortoiseshell, peacock, red admiral painted lady or comma butterflies, or the larvae of the garden tiger or mother of pearl moths. Secondly, take note of whether they are present individually or in a clump, as some species lay one egg at a time, while others lay all of their eggs together. So, of the five butterfly species listed above, only the comma, painted lady and red admiral will be found individually, the peacock and small tortoiseshell will be found in large clumps, usually beneath a silken 'tent' to protect them from predators. This can help you narrow down your identification.

When looking for caterpillars, bear in mind that some have evolved complex ways to protect themselves from predators. This may include hiding within its food plant, feeding at night and hiding by day, or covering itself in a silken tent that resembles a spider web. Make sure you know what you're looking for before you go out to find it, as this will help you locate even the trickiest of caterpillars.

If you find a caterpillar on the ground it's probably looking for somewhere to pupate. Make sure it's safe (away from the pavement or road) and take a photo of it. You can then look it up when you get home.

Bear in mind that this article relates to caterpillar identification in the UK – if you're looking for a caterpillar identification in another country, make sure you find a page or app dedicated to identifying caterpillars in that country.

Here is a selection of some of the most common species of caterpillar found in gardens.

Poplar hawk-moth (Laothoe populi)

Size: 65-70mm
Where to find them: on or near its food plant – look for them camouflaged, hiding beneath a leaf
What they eat (food plant): poplars (including white poplar), aspen and willows
When to see them: June to October

The poplar hawk-moth caterpillar has a sleek, plump, heavy body in bright green, sometimes with a glaucous blue or turquoise sheen, and slim, pale, diagonal flashes and pinkish spots along each side of the back. Pale-pink tail horn.

Elephant hawk-moth (Deilephila elpenor)

Size: 85-95mm
Where to find them: on or near its food plant
What they eat (food plant): willowherbs and fuchsias
When to see them: July to September

The elephant hawk-moth caterpillar has a bronze, brown to greenish body, with eye spots behind head and tail thorn. If disturbed it squeezes its front segments into a narrow trunk, inflating its eye-spots into a snake-like head.

Garden tiger moth (Arctia caja)

Size: 60-70mm
Where to find them: on or near its food plant
What they eat (food plant): a variety of food plants, including nettles, docks and hound's tongue.
When to see them: August to October, April to June

The garden tiger caterpillar has a black upper body and ruddy brown lower body, with long, pale hairs all over. A very hairy caterpillar, it's known as a 'woolly bear', and has a mesmerising undulating gait.

Cinnabar moth (Tyria jacobaeae)

Size: 25-30mm
Where to find them: on or near its food plant
What they eat (food plant): ragwort, occasionally groundsel
When to see them: May to August

The cinnabar moth caterpillar has yellow and black bars with sparse, long, pale hairs. It shreds its food plants to bare stalks, leading to local population crashes.

Vapourer moth (Orgyia antiqua)

Size: 35-40mm
Where to find them: on or near its food plant
What they eat (food plant): deciduous trees and shrubs, including cotoneaster and pyracantha
When to see them: May to September

The vapourer moth caterpillar is a psychedelic, animated boot brush, with prominent short, yellow or orange dorsal tufts, and a long, black head and tail whisker fluffs. Mature larvae can often be found resting on their food plant in late summer.

Mullein moth (Cucullia verbasci)

Size: 45-50mm
Where to find them: on or near its food plant
What they eat (food plant): mulleins, figworts and occasionally buddleia
When to see them: May to July

The mullein moth caterpillar has a plump, pale creamy-green body has yellow blotches and stark black spots. Heavy infestations will shed leaves to bare stalks. Poisonous, so feeds openly during the day.

Brown China-mark moth (Elophila nymphaeata)

Size: 12-15mm
Where to find them: in a floating leaf case, near its food plant
What they eat (food plant): pond plants such as frogbit, water plantain, or waterlilies
When to see them: all year round

The brown China-mark moth caterpillar is unusual among caterpillars, as it's completely aquatic. It has a smooth, pale-cream or beige body. On hatching, the larva mines inside a leaf, but as it matures it cuts and glues two oval leaf fragments with silk to make a floating case.

Drinker moth (Euthrix potatoria)

Size: 65-75mm
Where to find them: on or near its food plant
What they eat (food plant): common grasses such as cock's foot
When to see them: August to October, April to June

The drinker moth caterpillar looks like a gold and blue blanket, with short tufts of black along its back, and a frayed white skirt. Named for supposed habit of supping dew drops.

Holly blue butterfly (Celastrina argiolus)

Size: 15-18mm
Where to find them: inside the flower bud or berry of its food plant
What they eat (food plant): the flower buds, berries and terminal leaves of holly in spring, and ivy in summer/autumn. In gardens will also alternate between pyracantha and snowberry
When to see them: May to October

The holly blue butterfly has a squat, plump, silky-green body with tinges of pink. May be tricky to find as the larvae bore into the side of the bud they are feeding from, and eat it from the inside.

Browntail (Euproctis chrysorrhoea)

Size: 30mm
Where to find them: in a large silken web with its siblings
What they eat (food plant): brambles and hawthorn. Occasional fruit tree pest
When to see them: August to October and April to June

The browntail moth caterpillar is black, streaked with whitish marks down each side and two orange bumps near its tail. Each segment has hair tufts. Lives in a communal silk webbing ‘nest’ on its food plant – be careful touching this caterpillar as its fine hairs have been know to cause rashes and breathing difficulties in some people.

Comma (Polygonia c-album)

Size: 40mm
Where to find them: individually, beneath leaves, on its food plant
What they eat (food plant): hops, stinging nettles, elms and currants
When to see them: May to October

The comma butterfly caterpillar is black, with a back marked in orange (front) and white (back), especially pronounced nearing maturity, but blurred, and resembling a bird dropping when young.