30 Days Wild Blog - Day 4: Identify a caterpillar

30 Days Wild Blog - Day 4: Identify a caterpillar

What is a caterpillar?

A caterpillar is the larval stage of a moth or butterfly. It is the second part of their four-stage life cycle: egg, larva, pupa and adult. Caterpillars have long, worm-like bodies with six true legs. They can also have a variable number of stumpy false legs called prolegs which help them to move and cling to things. 

Caterpillars can change dramatically from when they first hatch to when they're ready to pupate. Some can increase their body mass 10,000-fold in just a few weeks - that's like a baby growing to the size of a sperm whale! Many look very different as they grow, so we've described the larger stages of the caterpillar's growth, when they're often more obvious.

Which caterpillars am I likely to see?

Many of these caterpillars are most obvious when they're fully grown and looking for a place to either pupate or settle down for the winter, though some are easily spotted on their favourite food plants. Here are some of the species we're most frequently asked to identify.

Drinker moth

When & where: August-June. A variety of habitats including gardens, but especially damp grassland, marshes and boggy areas.
Description: Up to 7 cm long. Dark and covered with brown hairs and golden speckles. A row of white hairs runs down each side of the body.


Fox moth

When & where: June-April, most obvious in spring. Common habitats include heathland and coastal grassland.
Description: Up to 7 cm long. Hairy, with long dark hairs on the sides of the body and shorter orange hairs on top. Young caterpillars are dark with orange bands.

Garden tiger

When & where: August-June. A wide range of habitats including gardens.

Description: Up to 6 cm long. An extremely hairy caterpillar, known as the "woolly bear". Mostly black and ginger, with longer white hairs.


When & where: July-September. Found on ragwort in most grassy habitats.

Description: The caterpillars of this moth are distinctive, with black and yellow stripes - warning predators that they taste terrible. They're easily spotted feeding on ragwort.


Privet hawk-moth caterpillar

When & where: July to September. Widespread in southern England and Wales. Found in a variety of habitats, including gardens.

Description: Up to 8.5cm long. Green and chunky, with purple and white stripes on the body and a black and yellow horn on the rear. 


Puss moth caterpillar

When & where: June to September. Widespread in a variety of habitats, including parks, gardens and wetlands.

Description: A plump, green caterpillar with a dark, white-edged 'saddle'. The head is surrounded by a pink patch, with false eyes making it look like a giant face. There are two thin tails.

Mullein moth

When & where: April-July. A range of open habitats, including gardens. Feeds on mulleins and buddleia. 

Description: Distinctive whitish caterpillars, with horizontal yellow splodges across the body and large black spots.