September: the Netted Carpet moth

Netted carpet moth

The netted carpet moth is one of the rarest moths in the UK. First recorded near Lake Windermere this moth can only be found at some sites in the Lake District and North Wales.

A fussy eater

Research has shown that this moth relies totally on touch-me-not balsam. This small delicate plant with yellow flowers is the only native species of balsam in the UK, but many invasive balsams are aggressively wiping this plant out. This means that the population of the netted carpet moth plummeted to near extinction in the 1980s and 1990s and has only recently begun to recover.  The perfectly camouflaged larvae of this moth feed exclusively on the plant.

Can you spot the caterpillar?
Touch me not balsam plant with camouflaged caterpillar
Can you spot the caterpillar?

Numbers of this moth are returning thanks to a partnership of many organisations. Here in the south Lakes the National Trust ranger team has been working hard to play their part in the return of this species to many areas.  By introducing cows to the favoured areas of the moth, research has shown that more aggressive plants such as Himalayan balsam are kept at bay, allowing the touch-me-not to flourish.  Our rangers have also been “pulling up” invasive species such as yellow balsam to make space for touch-me-not to return. 

A survey of larvae

I joined the ranger team and local experts to survey the population of larvae on the east side of Coniston Water. We started our search at Brantwood house (once home to John Ruskin) and continued our search along the shore of the lake. Each touch-me-not-balsam plant was checked for the tiny larvae by lifting up the leaves gently to try and spy the light green larvae. It’s delicate work, and they are incredibly difficult to spot at first, but you soon get used to finding the long green larvae stretched out along the stalks of the plant.

We spotted over 40 larvae in one clump of balsam alone! Few of these will survive and become the netted carpet moth, but it was fantastic to see so many areas were being well managed to give this species the best possible chance at survival.

A positive future for the netted carpet moth

The continued efforts of the National Trust, Butterfly Conservation and many other organisations as well as farm tenants has meant that now over one thousand netted carpet moths have been recorded on 56,000 balsam plants!