Garden Tiger Moth and its Woolly Bear caterpillar in serious decline

The very large and colourful garden tiger moth (Arctia caja), and its hairy caterpillar, which is known as a "woolly bear," were once very common in the UK but are now declining in numbers fast.

Arctia caja (Photo: Kurt Kulac)

The garden tiger has brightly coloured forewings that are patterned in creamy-white and chocolate-brown and the hind-wings are orange with blackish-blue spots. It has a stout, mainly orange body and a dark brown furry thorax.  The colours and patterns are very much given to variation too, although the moth is easy to identify.

This moth is found, as its name suggests, in gardens, but also on farms, in meadows, on railway and river banks and on sand dunes.  It has a liking for damp areas, though the caterpillars can often be seen crawling rapidly across paths and open ground on hot days.

The garden tiger moth emerges from late June to August. It used to be a very common and widely distributed moth in the UK but over the last 30 years its numbers have dropped by as much as 89%.  This is difficult to understand because its caterpillar will eat a very wide range of food-plants, including many weeds, such as docks and dandelions. It will also eat nettles and cultivated plants, such as rhubarb and cabbage. The caterpillar will feed on various shrubs, including the raspberry, blackberry and broom as well.

Garden Tiger Moth caterpillar (Photo: Acelan)

The garden tiger moth caterpillar is known as a woolly bear because it is covered in long black and ginger hairs. These hair are a good protection for the larva and can cause irritation.  The young caterpillars hibernate and feed up in the spring. It is thought that Climate Change and mild winters have caused the decline in this species, which has failed to adapt to the changes in the climate.

The adult garden tiger is so brightly coloured to warn predators that it tastes very bad and is toxic. The colouration and patterns are a very good example of "warning colours."

The garden tiger moth is one of many British moths and butterflies that have been declining in numbers and are no longer as common s they used to be, which is a worrying trend.