Status and Distribution
Very local with widely scattered records from across England north to Yorkshire, parts of western Wales, Ireland and Northern Ireland. New to VC69 Westmorland (south Cumbria) in 2019 (C. Lewis pers comm). Not noted in south-west England, Scotland, Isle of Man or the Channel Islands.
Bradley & Fletcher no:
Maps updated with all data received by January 2020.
Foodplant and Larval Feeding Signs
Eriophorum angustiflium (common cottongrass), see plant distribution map, although this plant does not occur at the moth's Wicken Fen site. Two specimens have emerged from the collected dead stems of a Scirpus sp. (club rush) on a saltmarsh in Essex but may not necessarily have been feeding as a larva on this.
Examples of feeding signs on common cottongrass in Holland can be seen at http://www.bladmineerders.be/nl/content/monochroa-suffusella-douglas-1850
The larva overwinters within the stems.
Fens, marshes and lowland raised bogs (mosses).
Finding the Moth
Larva: mines the stem and lowest parts of the leaves in the autumn, overwintering in the mine. In Spring it initially mines the reddish portion at the base of an overwintering leaf making an obscure, pale red, short, sinuous gallery in which the larva is invisible. It then moves into the green part of the leaf where the gallery becomes pale green and widens filling all or most of the width of the leaf (length 20-65mm). The larva and its greenish frass are still only barely visible and only when viewed from above. It appears not to change leaves and exits the leaf, once full fed, through a whole cut in the upperside of the leaf.
Adult: can be disturbed from cottongrass during the day, flies in the evening and later comes to light. Has been observed flying over pools at sunset before settling on grasses and cotton-grass.
There is some variability in the wingspan (10-14mm) and forewing grond colour (from whitish ochreous to a deeper ochreous colour). The palps are whitish ochreous mixed with some fuscous on the outer sides and is fuscous at the apex. On the forewing there is a black costal spot above a central blackish spot at three-quarters. When at rest on the cottongrass stems it resembles a Coleophorid moth.
Single brooded from late May to the end of July. There is one record from late August.
Earliest:6th May 1969 (VC11)
Latest: 25th August 1999 (VC9)
It has been suggested that the Wicken Fen moths fly slightly later than those elsewhere. This is not borne out by some of the records received from Cheshire, southwards to Hampshire (excluding Cambridgeshire) where it has been reported during the second half of July (17th to 30th) and even into late August (Hampshire).