I have had a few enquiries recently about people spotting small trees and shrubs covered with ‘webs or ‘tents’ full of caterpillars.
The picture is one example that I took whilst in Norfolk earlier this year. This particular example is of the brown-tail moth (Euproctis chrysorrhoea), a native of Britain and sometimes super-abundant.
Gardeners and others can be shocked by the damage.
The eggs are laid by the adult moths in summer and then live communally on trees and shrubs such as hawthorn, blackthorn, plum, cherry, rose and blackberry, and so are conspicuous in gardens in roadside landscaping schemes, or in this case on scrubby sand-dunes by the coast.
Because of the mass foraging behaviour with thousands of caterpillars totally defoliating individual shrubs and all covered in sheets of white webbing, these insects are often noticed.
Gardeners and others can be shocked by the damage, and the caterpillars that grow to be very hairy, can release irritating hairs that affect human skins and even breathing. If you spot them, then best to leave well alone!
The young caterpillars over-winter in web cocoons or hibernacula to emerge en masse the following spring.
This is when the massed larvae become very obvious. Very often the species concerned is one of the so-called ‘ermine moths’ – their wings looking like the ermine of medieval royal gowns.
One of my former students Karon Mayor sent me some pictures from Amsterdam where what appear to be ‘ermine’ caterpillars are busy stripping the city’s vegetation. These certainly are insects that get noticed and I recall the first time I saw them was taking a guided walk around Worsborough County Park in Barnsley many years ago. An entire hedgerow was covered from the floor upwards and for about 100 metres length.
A more worrying hairy caterpillar is that of the ‘oak processionary moth’ which is an alien, invasive species now established around Greater London. This causes immense damage to oak trees but also has huge ‘nests’ of caterpillars up in the tree canopy.
If disturbed the larvae release massed hairs that are carried in the air and can be seriously irrigating to skin, eyes and respiration.
Professor Ian D. Rotherham, of Sheffield Hallam University, researcher, writer and
broadcaster on wildlife and environmental issues