This is the caterpillar of the drinker moth (Euthrix potatoria) so called because the caterpillar is believed to drink drops of dew on grass stems.
They like damp and marshy places best, riversides and fens, but anywhere grassy will do; grasses, particularly cocks-foot and canary grass, are their main food plants.
This is a species that overwinters in its larval stage; the picture shows a caterpillar that hatched in July or August of last year. It hibernated in October when part grown, about 25 cm in length, and woke up in April this year.
Its distinctive tufts of hair, fore and aft, will already have developed by the time it went into hibernation. The hairs are an irritant and protect it from predators; take care if you handle a drinker moth caterpillar. In fact there is anecdotal evidence that it will use the hairs, or the chemicals that make the hair an irritant, in the structure of its cocoons.
This caterpillar feeds mainly at night, but despite this is particularly vulnerable to attack by parasitoid flies and wasps. During the day it can be found resting low down on vegetation.
It will become fully-grown, up to 7cm in length, by June. It will pupate, building a double walled papery cocoon on grass and reed stems, from which the adult will emerge in July. The adults are short lived; they lay their eggs during July and August, the eggs hatch after ten to twelve days and the new caterpillars set off to do it all over again.
Drinker moth populations have shown an encouraging recent recovery after a significant decline during the first part of the century.
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Southwick Country Park Nature Reserve 