THE MARSH MOTH ( H Y D R I L L U L A PALUSTRIS, HĂœBN.) IN EAST SUFFOLK WITH NOTES ON ITS RANGE AND OCCURRENCE IN THE BRITISH ISLES B A R O N DE W O R M S
THE capture on the night of 29th June, 1968, in Redgrave Fen of a female Marsh Moth (HydriUula palustris, Hiibn.) by Mr. C. W. Pierce and Mr. Geoffrey Burton is indeed a notable event in the annals of Suffolk lepidoptera, since not only is this the first occasion on which this very elusive insect has been obtained in the eastern part of the County but the female of this species has very seldom been obtained at light or by any other means than breeding. It is not the first record for Suffolk since two males were taken near Worlington on its western border by Mr. R. Demuth and Mr. A. W. Hughes on ISth June, 1932, with another in that immediate vicinity by Mr. Burton in 1936 (Morley: Memoirs, 1937, 24). So far as I am aware there are no other records for the County. The ränge of this species in the British Isles has always been something of a mystery. Barrett (v:266) mentions that the first certain capture was made by a Mr. Alliss just outside York in the early 1850's. while another was taken in Quy Fen, near Cambridge in May, 1862. Barrett himself secured the third specimen just outside Norwich on a gas-lamp in June, 1869. It was not tili 1877 that the species was obtained in some numbers, all males, in Wicken Fen which has remained one of its headquarters to this day. In 1898, over fifty examples were recorded from Wicken with a few from the nearby Chippenham Fen. Wicken continued to be its main stronghold tili the late Sir John Fryer and the late Mr. H. M. Edelsten secured it in Wood Walton Fen, Hunts, where the first larva was found in 1936, since its life history had never been established in this Country. By assiduous search thesc two pioneers discovered the secret of finding the larvae in the autumn, when full-grown, under heaps of decaying matter in the fen and published a most illuminating account of their researches and eventual success (Entomologist, 1944, 77: 65-72) with photos of the full-fed larva and of bred speeimens of both sexes. The diminutive female had hardly ever been seen since two were netted at dusk in 1896 and 1897 as far north as the neighbourhood of Carlisle. The secret of Palustris was at last known and thereafter larvae were obtained regularly, fed on meadow sweet and hibernated full-fed. Some fine bred series were obtained, in this way. One of the most assiduous in the hunt for these larvae was the late Mr. Geoffrey Todd of Norfolk who used to breed the species almost annually during the 1950's. Everyone who has tried these fen haunts towards the middle of June will appreciate how elusive this insect is especially at a light
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trap or sheet. T h e males usually only appear just singly between 1 and 2 a.m. and as often as not on a cold and foggy night. Doubtless there are many other localities where the Marsh M o t h exists in these Islands, though apart from this new Suffolk record Holme Fen also in Huntingdonshire seems to be the only other new haunt where it has been taken in recent years. It has yet to be found in the south and west of our Country. Even in Wood Walton Fen there are seasons when it is not taken and only a Single female seems ever to have been secured at light there. Its habits in the field are still imperfectly known, certainly in this Country. Abroad the Marsh M o t h has a very wide ränge from Southern to Northern Europe and sometimes it occurs far from a recognised marsh. I well remember in early July, 1958, when the males were the commonest species at light in a field of meadow sweet at Tvärmine, some miles west of Helsinki in Finland. T h e r e is still a good deal to be learnt about this moth and its capture in Suffolk will encourage field collectors to cast their nets in other possible areas in the Eastern Counties, and especially in the marshlands of the Lincolnshire coast.