This moth is highly secretive and unpredictable in its appearances. There is a noticeable size difference between the male and the female, the male being about one third larger. Both sexes have buff brown upperwings with those of the female appearing slightly darker. The underwings are pale, creamy-brown with darker veins. The female's thorax also appears darker brown than that of the male.
The marsh moth lays its eggs on meadowsweet and low-growing plants in the same habitats. The caterpillar feeds from June until September before overwintering. It pupates in April or May, and emerges from late May to June. Males will come to lights after midnight, but it has also been seen flying at dawn.
Once recorded from several counties in England, the marsh moth is now found only on two (but possibly four) sites in Lincolnshire. Previously, it was found in Huntingdonshire, Cambridgeshire, Norfolk, Suffolk, Yorkshire and Cumbria, with old records from Hampshire. The marsh moth is also found across most of Europe as far north as the Arctic Circle, and as far east as Siberia and Mongolia.
The marsh moth is listed in the UK Biodiversity Action Plan (UK BAP), and is included in English Nature's Species Recovery Programme. Because of its secretive and unpredictable appearances, it has been difficult to assess the true status of this species. At one site on the Lincolnshire coast, a method of monitoring the species has been to build piles of leaf litter, which attract the moth larvae and which seem to like the micro-climate As there are a large number of recorded historical sites for the marsh moth, it is intended that surveys for this elusive species will continue. It is also hoped that an 'ideal' habitat management regime for this moth will be established, based on the results of this monitoring.
The UK Biodiversity Action Plan for this species is available at UK BAP.
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