Recording Moths With Specialised Habitats:
Over the last few years (now in 1991) we have accumulated over 8,000 records of moths in the County of Cheshire on the 10Km square basis. A large proportion of these records are from garden traps and visits to varied habitats in squares that are obviously under-recorded. It has been clear for some time that this is leaving us weak in the recording of three groups of moths. The first, and perhaps most obvious group, are the day-flyers and this is just a matter of getting out and about at the right time. The other groups, closely similar in some ways, will remain elusive unless we do some "homework"; I am thinking here of species which inhabit a specific habitat type and seldom stray from it, and also of those species which are quite specific to one foodplant, and which seldom wander away from it and if it is uncommon and doesn't happen to grow where we are working we are unlikely to find them, perhaps I am being pedantic in trying to separate these into two groups but such distinctions may help to locate likely habitats.
This problem was highlighted by an experience in 1990. On 1st August, Eric Rudge and I made our first recording visit to the new Cheshire Wildlife Trust (CWT) Reserve at Holcroft Moss (SJ69). Almost the first thing we found was a couple of worn specimens of the Beautiful Yellow Underwing (Anarta myrtilli), a generally common heathland species. When I came to enter the record I was amazed to find that this was the only record we had between the Wirral (SJ38) in the West and Lindow Common (SJ88) in the East. Surely this little moth was not absent from the whole of the centre of the County? When on 1st September 1990 I joined Steve McWilliam at Runcorn Hill (SJ58) I soon swept the larvae of the species off heather there and a few days later got one at Bickerton Hill (SJ45) although the season was by then rather late for the species.
This was enough to show that we have been neglecting our heathland habitats; a glance at the records shows that other typical heathland species are also under-recorded; the Common Heath (Ematurga atomaria) is recorded from only 16 of our 31 10Km squares, the Ling Pug (Eupithecia goosensiata) from only 5, the Grey Scalloped Bar (Dyscia fagaria) from only 2, the Heath Rustic (Xestia agathina) from 7 and one or two others scarcely at all. An exception is probably the Narrow-winged Pug (Eupithecia nanata) which is more widespread and seems able to establish itself on smaller patches of heather such as a re grown in parks and gardens, although even this species was unrecorded in SJ58 until we swept at Runcorn Hill.
I think it is generally true that heather feeding species are only established where there is a good growth of the plant. The County Habitat Survey carried out by the Cheshire Wildlife Trust (CWT) in 1983 should have located every such habitat in the County, but clearly it did not as we were unaware of the existence of Holcroft Moss until it came to our notice that it was for sale! If we are to have a proper understanding of the distribution of heather feeding species we must first establish, on a map, a complete record of all sizeable areas of heather; for a start let's aim to map every habitat on which heather is the dominant plant over an acre or more (0.5 Hectares). This will start from the 1983 Habitat Survey which will have to be backed up by site visits and the personal knowledge of the nine Wildlife Trust Local Group Recording Officers. Can we achieve this by the end of April 1991 to get us out for the Spring emergence of the Common Heath ?
The only other Habitat Type that comes readily to mind is the Reed Bed of which there are certainly quite a number around the County (Cheshire), many of them conspicuous but difficult of access. Steve McWilliam's capture of both the Obscure Wainscot (Mythimna obsoleta) and the Fen Wainscot (Arenostola phragmitidis) amongst the reeds on the Moore Nature Reserve site (SJ58) shows what can be found, but these species will never be seen far from the reed-beds,very different from the Bull-rush Wainscot (Nonagria typhae) which evidently wanders far and wide and colonises any little patch of Typha growing on the edge of a pond. A few Phragmites plants growing along a ditch do not seem to attract the less common Wainscots so, once again, we need a County map showing every reed-bed an acre or more in extent; again the Habitat Survey should be a good starting point but we could allow ourselves a little longer as the Obscure Wainscot, the first on the wing, does not fly until June.
The desirability of locating good stands of particular plants, though in this case not the dominant plant in the habitat, is again best illustrated by example. I was on a Field Meeting of the Harrogate and District Naturalists' Society at Copgrove in 1964; at one point the leader, a botanist, pointed out that the white umbellifer growing at the side of the path was not Hedge Parsley but Burnet Saxifrage (Pimpinella saxifraga). My immediate reaction was to start searching the flower heads for the larvae of the Pimpernel Pug (Eupithecia pimpinellata) an insect that I had never taken. I soon had about a dozen larvae and bred a nice series! This moth is not on our current Cheshire list but Newton's Flora of Cheshire states that the plant is quite plentiful in some areas. This is just an example, one could go through the list and note probably a dozen or so species which are either seldom recorded, or even not recorded at all, but which depend upon a single plant species which is not particularly common and probably even less well known. If we have adequate records of the plants in Cheshire (and I believe we have) then we should take steps to explore them with very specific objectives in mind.
C. Ian Rutherford.