The larvae construct communal nests of white silk from which they crawl at night in single file, head to tail in large processions to feed on foliage in the crowns of trees, returning in the same manner.

Oak is its preferred food source, but the moth also eats the leaves of hazel, hornbeam, sweet chestnut, birch and beech.

[1] The nests may be hemispherical, teardrop shaped, bag-like, and blanket-like (surrounding part of a trunk or branch), and may be at any height on the tree.

[1] The caterpillars are mostly found in oak trees or on the ground under them in late spring and early summer, and do not live on fences, walls, etc.

The eggs arrived on oak imported to the Richmond and Ealing areas of London in 2006[4] and the range of the species in the UK has been steadily expanding despite efforts to eradicate it.

[6] The backs of older caterpillars (3rd to 6th instars) are covered with up to 63,000 pointed defensive bristles,[citation needed] sized between 0.2 and 0.3 millimeters, which contain an urticating toxin, the protein thaumetopoein.

[7] These setae break off readily, become airborne and can cause epidemic caterpillar dermatitis (lepidopterism), manifested as a papular rash, pruritus, conjunctivitis and, if inhaled, pharyngitis and respiratory distress, including asthma or even anaphylaxis.

It has been found that the skin irritation and itching caused by contact with these hairs can be largely eliminated by the use of cetirizine-based antihistamine tablets.

One alternative is to adopt a grass mulching technique to reduce possible contact, and to speed up the biological breakdown of the irritant hairs.

Sightings of these caterpillars in other areas should be reported to the Forestry Commission,[10] whose research agency issued guidance on the way to contain outbreaks and deal with infestations, so as not to increase the risk to the public.

On 15 July 2019 strengthened measures on the import of most species of oak into England were introduced to protect native trees from the threat of the pest.