90
Suffolk Natural History, Vol. 34
NOTES AND COMMENTS ON SOME SUFFOLK MOTHS IN 1997 M. R. HALL The general pattern of cold and inhospitable spring weather that seems to be the norm in East Anglia at the moment was repeated in 1997 with the exceptionally sharp frost on the night of April 20th being harmful to many of the early season species of moths. Nevertheless during the year there were one or two particularly exciting highlights and, as usual, many interesting records. It was very pleasing to discover several new stations for the shaded fan-foot, Herminia tarsicrinalis. This species, which was first recorded in Britain near Thorpeness in 1965 and until comparatively recently had not been found in any other county, was recorded at Nacton (SMG) and at more than one site at Purdis Heath (NS/SN). With the burgeoning activity in moth recording within Suffolk it is highly likely that this moth of open woodland that flies in late June and July will be found at an increasing number of localities across the county. Probably of greater interest was the discovery of the Oecophorid Tachystola acroxantha (Meyr.) by Jon Nichoils in Felixstowe (see separate paper). During 1997 this Australian species was also recorded by Edmunds and Parfitt (Ent. Ree. 110: 83) for the first time in North Hampshire, some 30 miles from the coast, so perhaps it will be found further inland in Suffolk in the near future. Another recent addition to the Suffolk list, the least carpet, Idaea vulpinaria atrosignaria, was again well represented at Felixstowe (JN) and now seems well established in this part of the county. Pleasingly several other species were also recorded in good numbers across the county and show that at least some of our moth fauna is flourishing at the moment. Several of the species that have been recorded in good numbers during 1997 are ones that were also seen in comparative abundance in 1996 and 1995. Species like the large nutmeg, Apamea aneeps; Shoulder stripe, Anticlea badiata, and creamspot tiger, Arctia villica britannica, all occasioned comment for their profusion. Similarly Blair's shoulder-knot, Lithophane leautieri hesperica, and Vine's rustic, Hoplodrina ambigua, are becoming increasingly numerous and widespread across the county. Several recorders commented on the abundance of the flounced rustic, Luperina testacea, and the latticed heath, Semiothisa clathrata, was far more numerous than in recent years. This latter species which occupies a ränge of habitats from downland and heathland to open woodland, waste ground and fenland - in fact anywhere where the larval foodplants (clovers, trefoils, vetches, lucerne and other legumes) are to be found - has always been widespread and locally common but numbers seen in 1997 were much higher than expected. Following its re-appearance at Nowton last year the dotted rustic, Rhyacia simulans, was recorded at Barrow (AP), Eye (PK) and just across the county boundary at Great Fen, South Lopham (MH) in 1997. These few records could well indicate that after several years of Virtual oblivion in the eastern counties this species is Coming up to a period of much greater abundance (a characteristic for which it is renowned) and it is certainly a moth that recorders should keep a keen eye out for in the next few years. Another species which has proven fluetuations in numbers is the garden dart,
Trans. Suffolk Nat. Soc. 34 (1998)
NOTES ON SOME SUFFOLK MOTHS, 1997
91
Euxoa nigricans, and this was much more in evidence in 1997 than of late, although it is generally regarded as being more common in the eastern counties than elsewhere in Britain. Not so the square-spotted clay, Xestia rhomboidea, which has always been described as an insect of deciduous woodland and is regarded as very local and rather elusive. This species was reported as being far more numerous than usual at Nowton and in the King's Forest (RE) with other specimens being recorded at Thornham (MH), Barrow (AP), Brandon Country Park (MH), Sicklesmere (SD) and several Breckland sites (SD). A species that is worthy of mention more for the numbers recorded at one particular site than for its overall abundance (although it has featured more regularly in reports during the last couple of years) is the marbled beauty, Cryphia domestica, of which 250 were recorded in July and August in a Heath trap in Ipswich (SL). The marbled beauty seems to have no ecological preference and flies from the end of June to August with a partial second brood later in the autumn. The larvae feed on Lecidea confluens, a crustaceous liehen which dots over old walls with its cracked and weather-beaten patches (and also other minute lichens which grow upon walls), both before and after overwintering in a silk and grit tunnel spun among the foodplant. After hibernation the larva secretes itself in this tunnel (which has been referred to as a "sand nest") during the day, having been out to feed in the early morning and retiring soon after 9.00 a.m. The tubercles of the Lecidea are the chief attraction being gnawed, removing the black crusts, to expose the white undersurface to view. These depredations are readily seen in the morning as the white tops are very conspicuous in the sunshine. Unfortunately it is not all good news and, as in past years, there were a number of species that were noticeable by their absence (or Virtual absence). Yet again many of the autumn flying moths, particularly the canary-shouldered thorn, Ennomos alniaria, and the September thorn, Ennomos erosaria, were very sparsely represented in county records. Although recorded at Aldeburgh (TP), Mettingham (MB), Redgrave (SMG), Pipers Vale (SMG), Purdis Heath (SN/NS), and in Breckland (SD) the drinker, Euthrix potatoria, was nowhere seen in its usual numbers and was generally scarce or absent. Several recorders reported that it was even less in evidence than last year when the current decline first caused comment. For a species that has always been regarded as locally common along hedgerows, in grassy rides in woods, fens, reedbeds and rough pasture, and one that is not renowned for population fluctuations, this decline (if more than a brief aberration in its usual abundance) could indicate a change in its overall behaviour or herald a more serious concern for moths in general. In addition to the white ermine, Spilosoma lubrieipeda-, lunar marbled brown, Drymonia ruficornis; and white-pinion spotted, Lomographa bimaculata, whose decline in 1996 continues, many of the prominents and the usually prolific poplar hawk-moth, Laothoe populi, were noticeably scarce in most traps. Regrettably three normally widespread and numerous noctuids have also joined the ranks of declining species. These are the flame Shoulder Ochropleura plecta, which has been common in a Wide ränge of habitats with the larvae being polyphagous on herbaeeous plants; the small square spot, Diarsia rubi, which again is regarded as common throughout the British Isles
Trans. Suffolk Nat. Soc. 34 (1998)
92
Suffolk Natural History, Vol. 34
with larvae feeding on a variety of herbaceous plants such as dandelion, dock, plantain, chick-weed, heather etc., and the nutmeg, Dicestra trifolii, a moth that is common and well distributed in south-east England and East Anglia but becoming more local to the west and north. The larvae of the nutmeg feed mainly on plants of the Chenopodiaceae family and the species is liable to population explosions which may be caused by the rapid increase of the foodplants on newly cleared ground. This feature may help to explain the current decline as such population explosions are frequently followed by a similar , but delayed, increase in parasites and it is only after a period of fairly extreme fluctuations that host and parasites settle down in balance again. Whilst such an increase in numbers for the nutmeg was noted a year or two ago this was not recorded for the other species currently in decline but nevertheless could, hopefully, explain their current status. As well as species that would seem to be generally increasing (or declining) there are others that are noticed more frequently for reasons more to do with recording techniques. Day-flying moths come into this category and many of such species are almost certainly much more numerous and widespread than present records would indicate. The lunar hÜrnet moth, Sesia bembeciformis, was reported from Ipswich (NS) and it is one of the clearwings that is more regularly recorded. There are others that are equally common, particularly the currant clearwing, Synanthedon tipuliformis, which are hardly if ever reported. The common heath, Ematurga atomaria, did occur on several record sheets as a prolific day time sighting and also from a moth trap at Barrow (AP). The common heath flies in May and June (and again in August) and should thus occasion more than the periodic record. It is perhaps more understandable that another day-flying species of heathy areas and open birch woods, the orange underwing, Archiearis parthenias, is under-recorded as it flies in March and April and is usually high up among the birches. It was recorded from around Ipswich by Neil Sherman but surely it is at many other locations across the county. Early season recording (in February and early March) confirmed the small brindled beauty, Apocheima hispidaria, is still flourishing at Thornham (MH) and is also well established along the Peddar's Way at Knettishall Heath (MB). This latter site is not the typical woodland or parkland more usually associated with this species and could indicate a much wider distribution just waiting to be verified by intrepid and hardy moth recorders. A little later in the year at the beginning of April the sloe carpet, Aleucis distinctata, was discovered in the north of the county at Stuston (MH) on extensive blackthorn thickets that are, however, only around 50 years old. With another record at the end of March from Brantham (DN), together with records from earlier years, it could be that this local species is waiting to be found in suitable habitats right across the county even though it is at the northem limit of its ränge. Another species that in Suffolk is also at the northem limit of its ränge is Mathew's wainscot, Mythimna favicolor. This species, which is unknown outside England, is locally common in salt-marshes where the larvae feed mainly on the common salt-marsh grass, Puccinellia maritima, and was recorded from Landguard (NO), Minsmere (CA) and Havergate Island (SMG) in 1997. It is quite likely
Trans. Suffolk Nat. Soc. 34 (1998)
NOTES ON SOME SUFFOLK MOTHS, 1997
93
that M a t h e w ' s wainscot occurs on other salt-marshes around the more southerly coasts and estuaries of Suffolk although it is similar to the common wainscot, Mythimna pallens, (and regarded by some as merely a saltings race of the common species) and can be confused with this species. The benefits of all the year round recording were shown by the unusual record of a plumed prominent, Ptilophora plumigera, at Monks Eleigh (AW) late in February as this species is not normally seen later than December. The knot grass, Acronicta rumicis, which is perhaps somewhat less numerous than some other members of the genus although it is still well distributed throughout Britain and regarded as common, has been more in evidence in species lists from 1997. There were records from Pipers Vale in Ipswich (SMG), Alder Carr Farm (SMG), Minsmere (CA) and Thornham (MH). Similarly the white-line dart, Euxoa tritici, which, although also widely distributed throughout the British Isles, is said to be more associated with heathland and coastal sandhills has been more in evidence this last year. The majority of the records were not exceptional in being from preferred habitats with sightings at Sizewell Belts (SMG), Minsmere (CA), Wortham (MH), Sicklesmere (SD), a number of Breckland sites (SD) and Barrow (AP) and also three different parts of Ipswich and its environs (SMG), (SL), (NS/SN) but several of the recorders commented on the unusually large numbers of individuals seen. Another species more specifically associated with the edges of coastal marshes in Suffolk, the rosy wave, Scopula emutaria, was recorded at both Minsmere (CA) and Havergate Island (SMG) in 1997. Morley regarded this species as "quite local, but by no means very rare along the coast" but it seems only to have been recorded at Walberswick in 1963 and Minsmere in 1989 since his day, so two records in one year (and from different sites) is most encouraging for the continued survival of the species in the county. The feathered ranunculus, Euchmichtis lichenea, whilst still well represented at its known coastal sites seems to be progressing a little further inland. Previously it had been noted at Purdis Heath and in 1997 twelve were recorded at Oxford Road, Ipswich (SL) and four at Nowton (RE). These records together with another four from just across the county border at Scole in Norfolk (MH) and an earlier singleton at Barrow (AP) in 1992 may indicate an expansion in the ränge of this species. The mullein wave, Scopula marginepunctata, which is mainly a coastal species, was recorded at Little Blakenham Pit (SMG) in August. It is found inland in the London area and with larvae feeding on mugwort, yarrow, plantain and other low growing plants it could be another species that is moving inland in Suffolk. A record of the Kent black arches, Meganola albula, from Minsmere (CA) confirms that this generally distributed but local species is still to be found at sites along this Stretch of the Suffolk Coast. Not all moth recording relies on finding the adult, either by night or day, and for many of the smaller moths it is frequently easier to find the larvae. One such species is the bagworm Psyche casta which was spotted in Raydon Great Wood (SzN). In this and several related species the larvae construct a silken case and decorate the exterior with various materials. The shape of the case, the material used to Camouflage it and the way in which it is attached are
Trans. Suffolk Nat. Soc. 34
(1998)
94
Suffolk Natural History, Vol. 34
characteristic for each species. With Psyche casta the larval case is covered with pieces of grass-stem attached longitudinally. A very good description of the case, with illustration, and an insight into the life history of the moth is to be found in issue number eight of the newsletter of the Suffolk Moth Group. The species was also seen at Brandon Country Park (MH) but surely it and at least three or four of its relatives are to be found elsewhere in Suffolk. Several other micros were indeed recorded at light and perhaps the most worthy of mention are the willow ermine, Yponomeuta rorella, recorded at Needham Lakes (SMG) and Acleris lorquiniana, which was noted at Redgrave Fen (AW). The former is found from Devon to Northumberland but mainly in the seaboard and eastern counties. It is of sporadic appearance being an occasional migrant which becomes temporarily established. This is believed to be a new county record. The latter is a Tortrix moth which is a little unusual in being one of only five species in the genus Acleris to be bivoltine, the other 23 being Single brooded. The larvae of the first generation feed on the young shoots of Purple Loosestrife and those of the second generation feed in the flower spikes, eating the flowers and seeds. It is locally abundant in the fens and broads of Norfolk and Cambridgeshire but this is almost certainly the first Suffolk record (Morley commenting that it was a Norfolk species to be expected in Suffolk). Also recorded at Redgrave Fen on the same night in July was another Tortrix, Lobesia adscisana which is restricted to the south, south-east and eastern counties of England. It is associated with rough meadows, waysides and waste places with the larvae living in the shoots of the Creeping Thistle. A micro that is said to be less common than formerly, Sitochroa verticalis, was recorded at Icklingham (TP) in June. It is probable that this was an immigrant as it is known that the resident population is periodically reinforced by migrations. There were fewer migrants reported in 1997, in terms of both species and numbers, than in either 1996 or 1995. Probably the most spectacular was the convolvulus hawk-moth, Agrius convolvuli, recorded at Nowton (RE) and one of the most attractive the orache moth, Trachea atriplicis, from Landguard (NO) in July. The orache was once a resident British species and probably one of the last known native specimens was taken near Stowmarket in 1915. In August Dewick's plusia, Macdunnoughia confusa, was recorded at Landguard (NO). Although this eastern Palaearctic species has been recorded at least twice in Norfolk since the first British record in 1951 (at Bradwell-on-Sea in Essex) this is the first time it has been seen in Suffolk. The other migrants reported were the white point, Mythimna albipuncta, (RE), (CA), (SD), (SMG); the delicate, Mythimna vitellina, (RE), (NO); tawny wave, Scopula rubiginata, (SL), (NS), (CA); marbled clover, Heliothis viriplaca, (TP); dark sword grass, (RE), (AP), (SD), (NS), (SMG); the diamond-back moth, Plutella xylostella, (SL), (NS) and the silver Y, Autographa gamma. This is probably the most regularly reported migrant each year and 1997 was no exception with a dozen recorders noting the moth from sites across the county. It was the comments on numbers seen that were exceptional - five in 1997 compared with 58 in 1996 and the lowest number for eight years at Barrow (AP); only 49 at Nowton (RE) and 38 in 1997 compared with 745 in 1996 at Sicklesmere (SD). As in earlier years I am sure there have been other sightings of migrant
Trans. Suffolk Nat. Soc. 34 (1998)
NOTES ON SOME SUFFOLK MOTHS, 1997
95
moths but both the numbers and variety of species were obviously well down on the two previous years and if records are not sent in to either the county recorder, Jon Nicholls, or the Suffolk Biological Records Centre (or to me), where they can be verified if necessary, they cannot be included in this report. Do please send records for inclusion in future reports either to Jon Nicholls, 18, Berners Road, Felixstowe, Suffolk, IP11 7LF, or to the Suffolk Biological Records Centre, c/o The Museum, High Street, Ipswich, Suffolk, EP1 3QH. As you can see from the above the Suffolk Naturalists' Society has a new county recorder for moths and I would like to take this opportunity to thank the retiring recorder, Arthur Watchman, for all his help and advice over the last decade or so. In the years since I took over from him the writing of these notes Arthur has always given freely of his experience and advice and his long term knowledge of Suffolk moths has been invaluable. I know that in Standing down as county recorder he is by no means giving up his interest in moths (nor the many other aspects of wildlife study he so enjoys) and I look forward to benefiting from his expertise and friendship for many years to come.
Acknowledgements I thank all the recorders whose records and notes have helped to compile this report: Charlotte Anderson (CA), Maggie Brooks (MB), Paul Kitchener (PK), Stuart Ling (SL), David Nash (DN), Jon Nicholls (JN), Suzanne Nicholls (SzN), Steve Noye (SN), Nigel Odin and Mike Marsh (NO), Tony Prichard (TP), Neil Sherman (NS), Suffolk Moth Group (SMG) and in particular Stan Dumican (SD), Rafe Eley (RE), Adrian Parr (AP), and Arthur Watchman (AW) whose additional comments on numbers and local fluctuations have been so helpful. I am also indebted to Rafe for letting me know that he recorded a marbled green, Cryphia muralis, in his garden trap at Nowton on 18th September 1985 and so my remarks last year (Trans. Suffolk Nat. Soc. 33: 51) about previous Suffolk records for this species were incorrect, for which I apologise. M. R. Hall (MH) Hopefield, Scole, Diss, Norfolk, IP21 4DY.
Trans. Suffolk Nat. Soc. 34
(1998)