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NEWSLETTER No. 42 -  Spring 1999

WEST MIDLANDS BRANCH, BUTTERFLY CONSERVATION

 

Moths of the Wyre Forest Royal Ordnance Site

Although the Wyre Forest has received regular attention from Lepidopterists, recording of this huge area has always been patchy and many parts remain unrecorded, especially in the Shropshire Wyre. In consequence, I was most enthusiastic when I heard of plans to conduct a survey of moths of the Royal Ordnance compound at Postans Plain in the north-eastern sector of the Forest; so one night early in June 1997 I arrived at the compound to meet a group of fellow moth enthusiasts and have a first look at the site, which is normally out of bounds to the public.

The Royal Ordnance compound consists of a large clearing straddling a shallow valley and surrounded by mature, mostly oak, woodland through which runs the site's boundary fence. Within is an open hillside which is kept closely mown by the site staff and which supports an acidic heathland community with abundant low heather plants. Surface drainage makes parts of the hillside treacherous under foot; the slope drains into a shallow stream which bisects the compound and is flanked by a belt of lush herbage, and a dam on this stream has created a small pool. Around the site offices and outbuildings there is regenerating scrub consisting chiefly of birch, sallow and bramble.

It was quickly obvious that the Royal Ordnance site is an ideal one for a moth survey; there are several electricity power points scattered around the compound which, with the “dalek-style” extension leads on hand, allow us to run half a dozen mercury vapour traps across a wide area. In addition, Royal Ordnance has its own bright outdoor lighting under which we can stretch white sheets. The result is as much pulling-power as is possible to imagine for catching moths.

The survey team consists of ten or so members of Butterfly Conservation and friends, from Worcestershire, Shropshire and the West Midlands, who meet on the first Friday of each month in season to purvey the “black arts" of moth trapping. We made five site visits in 1997 and six in 1998 and to date have recorded about 275 species, of which 70 are microlepidoptera. We have found on this site a moth fauna every bit as rich as anywhere in the Wyre, with an impressive range of species local or uncommon in the Midlands.

The best represented element of the Royal Ordnance compound's moths is that of mature deciduous woodland with oak, birch, poplar and sallow being the major larval foodplants. The mouth-watering list of moth species of this habitat type is long and includes the Angle-striped Sallow, Alder Moth, Marbled and Lunar Marbled Browns, Barred Hook-tip, Olive, Satin Lutestring, Oak Nycteoline, Brindled White-spot, Blossom Underwing, Frosted Green, Maiden's Blush, Clay Triple-lines and Blotched Emerald. Not only are the species themselves impressive, but they are sometimes in amazing numbers; we have lured Lobster Moths on several occasions, and have single-night maxima of twenty Green Silver-lines, 25 Brindled Pugs and over 40 Great Prominents.

Almost as well represented in our traps are moths of the woodland floor herbage. Some of these have very specific foodplants such as the Speckled Yellow (on Wood Sage) and Rivulet and Small Rivulet (on Red Campion); but many more feed on a range of herbaceous plants and grasses, and include Grey Arches, Slender Brindle, Purple Clay, Single-dotted, Cream and Satin Waves, Little Emerald and Marbled White-spot. Larvae of the Fanfoot and Common Fanfoot feed on withered leaves; the latter has declined nationally so alarmingly in recent decades that it is decidedly uncommon, with the Wyre as its stronghold in our region.

The open heathland and grassland in the compound undoubtedly adds to the diversity of species on site. We catch True Lover's Knots a-plenty about the heather, and the Scarce Footman's numbers belie its name! Narrow-winged Pug, Neglected Rustic, Feathered Gothic, Plain Wave, Straw Dot, Antler, Small Purple-barred and Small Elephant Hawk are all characteristic of this habitat. In the damper, lusher valley bottom we often find Common Wave about the sallows, and the Ear Moth, Small Wainscot and Red Chestnut occur in damp grassland.

The last main habitat type reflected in the moth fauna of Postans Plain is coniferous woodland. Although this is not well represented in the compound itself a conifer plantation abuts its southern border and is doubtless the source of our several records of Pine Carpet, Spruce Carpet, Barred Red, Bordered White, Larch Pug and Tawny-barred Angle.

As my personal interest is in the Lepidoptera of Shropshire I have been particularly pleased to add several significant records to the county list from our work on the Royal Ordnance site. Black Rustic in 1997 was a first for the Shropshire Wyre and the discovery of good numbers of Marbled White-spot shows that it still breeds in the county - there had previously been only one record since the turn of the century. A Black Arches and a Waved Black were only the second and third county records respectively.

Although none of the macros recorded so far in the survey have been firsts for Shropshire, two micros were: Cochylis roseana, whose larval foodplant, Teasel, grows locally in abundance, and Scoparia ancipitella, a rather little-known Pyralid. In general the diversity of microlepidoptera reflects the same habitat types as that of their larger cousins: that is, deciduous woodland (e.g. Phyllonorycter roboris, Aleimma loeflingiana, Phycita roborella); heathland and grassland (Neofaculta ericetella, Acleris hyemana, Agriphila geniculea); damp habitats (Bactra lancealana, Evergestis pallidata, Perinephela lancealis); and coniferous woodland (Rhyacionia buoliana, Dioryctria abietella). However, some micro species represent habitats not exploited by the macros; so we have encountered for example Pyralis farinalis, whose larva feeds on cereals and cereal waste, Blastobasis lignea which lives on decaying organic matter such as bird-droppings, and Elophila nymphaeata, the Brown China-mark, which has an aquatic larva and which, judging from its regular appearance at our lights, lives in good numbers in the pond.

There is much still to be done at Postans Plain: 275 species hardly represents half the potential moth fauna of the Royal Ordnance site. Nonetheless, we have achieved much already in our two survey seasons; for which, thanks to all who have taken part in the survey, to Frank Lancaster for initially securing us access to the site, and to the staff of Royal Ordnance themselves for their patience, help and interest in our strange nocturnal activities!

Godfrey Blunt 11th January 1999