Social Pear Sawfly Neurotoma saltuum

Hawthorn Moth caterpillars
Hawthorn Moth caterpillars
Shown is the larvae of Neurotoma saltuum, also called the Social Pear Sawfly. Many thanks to John van Roosmalen, Validator Moths on observation.org, The Netherlands for the ID. Usually found on pear or hawthorn, the amber-coloured larvae are surprisingly large for a sawfly. They live in dense colonies within a silk web on their foodplant.
Hawthorn Moth caterpillars and silk web
Hawthorn Moth caterpillars
Hawthorn Moth caterpillars
The larvae make the silk web to protect themselves from predators, both birds/small mammals and parasitoid wasps/flies.
Hawthorn Moth caterpillars
Hawthorn Moth caterpillars
Hawthorn Moth caterpillars
Their habits and habitat are similar to those of the smaller Hawthorn Moth Caterpillar, Scythropia crataegella, also often found in dense webbed tents on hawthorn, blackthorn and cotoneaster. The thorns provide additional protection.
Hawthorn Moth caterpillars
Hawthorn Moth caterpillar webbing on hawthorn sapling
Hawthorn Moth caterpillars and web
The larvae 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.