The Netted Carpet moth is one of Britain's most endangered moths and the Lake District is its only stronghold. It was heavily collected by the Victorians and thought to be extinct early in the 1900's. It was rediscovered in 1945. Twenty years ago the species was known from about 25 locations in the area, but current estimates suggest that up to half of these sites no longer support the moth.

The larvae of the moth feed exclusively on touch-me-not Impatiens noli-tangere which is itself a scarce plant in Britain, also with a Lake District stronghold. The plant grows in damp woodland, usually besides streams where nutrient rich silt has accumulated, by wet roadsides and timber extraction sites. The main colonies occur in the area between Coniston Water, Lake Windermere and the Rusland Valley. A part of the garden at Ruskin's house, Brantwood, on the east side of Coniston is managed with the species in mind.

Touch-me-not is an annual plant and its numbers fluctuate year by year depending on the degree of successful germination. Unfortunately recent wet springs, with extensive flooding, have led to poor germination and a drastic fall in the number of plants at many sites. Its ecology is not well understood; attempts to germinate the seed give poor results. In the natural state it turns up in recently disturbed ground, often at roadsides where vehicles have damaged the edge. Further research into the ecology of the plant is much needed. Not surprisingly, the Netted Carpet moth has suffered similar declines in abundance.

The National Trust is investigating ways of encouraging the foodplant to grow more successfully, initially by some tree cutting to reduce the shading which has occurred at many sites. Since 2003, the Trust has also managed some of the woodland around Coniston Water with the use of a small number of a traditional breed of cattle, the Blue Grey. When fed supplementary hay scattered in the woodland, the cattle trample the ground. This helps the spread and germination of the seed. Cattle are removed before germination takes place. At one site the number of Touch-me-not-Balsam plants increased from 880 to 56,000 over a four year period, with the result that the number of Netted carpet larvae counted rose from 45 to 565.

Research by John Heath (of the ITE) in the 1950's suggested that, in addition to the presence of its foodplant, the Netted Carpet moth requires a habitat having at least 150 cm annual rainfall. His experiments indicated that in drier conditions the pupae died before emergence or pupal emergence was prevented. The yellow-green larvae may be found on the underside of the leaves, well camouflaged by the ribbed veins of the leaf.

The moth is on the wing throughout July and into August, while the plant produces its brown-spotted yellow flowers throughout August. It does best in sunny sites where there has been some soil disturbance.

The small tortrix moth Argyroploce penthinana used to be found on the same foodplant. The dirty white larvae fed and pupated within the stem, from which they could be bred on by collecting the stems in winter. It would be interesting to see whether this species has hung on, as did the Netted Carpet early last century, despite not having been recorded in recent times.

Please report any sightings of the foodplant (or moth).