The small white Hawthorn Moth with brown markings is named after the main foodplant of its caterpillar stage, as is often the case. The moth is prevalent over most of temperate Europe and, in the UK, most of England and Wales. The amber-coloured caterpillars are surprisingly large for such a small moth. They live in dense colonies within a silk web on their foodplant.
The caterpillars make the silk web to protect themselves from predators, both birds/small mammals and parasitoid wasps/flies.
Those shown here are feeding on their usual foodplant, a hawthorn sapling, but they are also known to use blackthorn and cotoneaster. The thorns provide additional protection.
The caterpillars make quite a mess of the host bush, not only defoliating it but also leaving the webbing and frass (droppings) on the branches they have stripped.