Caterpillar Webs Engulf Hedgerow As Spring Ermine Moth Activity Begins

A U.K. photographer was surprised when he discovered a hedge completely covered in caterpillar webs.

Mick Hickman was walking along a road near Bawtry in the English region of South Yorkshire on June 1 when he passed by a whole section of hedge that appeared white rather than green.

At first, Hickman was creeped out because he thought the webs were from spiders.

However, upon closer inspection Hickman found the hedgerow covered in ermine moth caterpillars that had produced the webs.

He told the BBC: "I could see nothing but web over a large area. It went down the hedgerow, across the grass and even on to concrete in some places."

Phil Sterling, an ecologist from the Butterfly Conservation charity, told the broadcaster there could have been tens of thousands of the caterpillars in the hedge.

He added ermine moth caterpillars construct the webs as a form of protection and that they cause no danger, saying: "By the end of July, it will be like the caterpillars weren't there."

Others spotted what appeared to be caterpillar webbing in rural hedges elsewhere.

#Springwatch a patch of roadside rural hedge covered in thick webs/nets containing these caterpillars? Can you identify them please and explain what’s happening? Thanks @BBCSpringwatch

— Jane (@janeretallack) June 3, 2021

The U.K.'s Forest Research government agency states small ermine moth caterpillars will begin feeding during the spring and are fully grown by around June, by which time they will form silk webbing before pupating into adults.

Forest Research states the webbing can cause alarm but that "even in extreme cases it should not affect the long-term health and vigor of the plants." It adds there is no need to control small ermine moths.

Adult ermine moths tend to be active during July and August, in which time they mate and lay eggs. The eggs hatch and the larvae spend the winter as caterpillars.

Occasionally the caterpillars' webbing makes headlines when populations are particularly conspicuous.

In 2013 an entire avenue of trees on Jesus Green in Cambridge, U.K., became draped in ermine moth caterpillar webs, spooking at least one resident who told The Guardian: "It really gave me the creeps."

The phenomenon of vegetation being covered in webs has also been observed in the U.S. In one case that took place in Iowa last year, the cause really was spiders.

Users took to Twitter to post photos they had taken in November of spiderwebs covering trees and grass in the state. It was reported that temperature fluctuations had caused millions of spider eggs to hatch months earlier than they were supposed to.

Who can tell me what is going on with these spiders hatching in Iowa today?

— MrsKultScience (@MrsKult) November 5, 2020

Donald Lewis, an entomology professor at Iowa State University, told the Des Moines Register: "These spiders are not dangerous and this outdoor spider phenomenon will not affect your health or wellbeing."

Caterpillar webs
A stock photo, taken in Germany, shows ermine moth caterpillars on a web surrounding leaves. Immature caterpillars begin feeding in the spring. U. J. Alexander/Getty