Llanelli Naturalists Newsletter - Winter 1992/1993
Ian Morgan

A couple of small tortoishell Aglais urticae butterflies, feeding at dandelion flowers and enjoying spring sunshine at Erw-las, Llwynhendy 21/537993 on 4 March launched the 1992 butterfly season, but subsequently there was a wait of almost a month before warmish weather on 8/9 April brought out the vanguard of peacocks Inachis io and commas Polygonia c-album from hibernation at various south Carmarthenshire localities. The comma is reputed to overwinter for example amongst dense ivy on walls or tree trunks but, because of its cryptically-coloured crenulate wings, it is almost impossible to find.

By the 18th April, both speckled woods Pararge aegeria and orange tips Anthocaris cardamines had joined the peacocks and commas (though small tortoishells were rarely seen) and the first migrant - a painted lady Cynthia cardui was observed at Pembrey Forest 22/403018. Painted ladies were later seen (in usually small numbers) throughout the summer to mid October and one at Machynys on 23 June was watched as she laid eggs on spear thistle Carduus vulgaris. Dainty holly blues Celastrina argiolus emerged by the 3rd of May in the author's garden, with individuals characteristically flying quite high off the ground - an useful "fizz" factor for recognition later in the season when the more low-flying common blues Polyommatus icarus are around. Holly blues were also recorded later (on 24 July), by Graham Motley near Gallt-y-Berau 22/771458. There were two records (both by Andrew Lucas) of green hairstreaks Callophrys rubi in the second half of May - a singleton at Cors Carmel 22/594155 (18/5) and many on the brackeny and gorse-clad 'heath" of Marros Mountain 22/208092 (27/5). Its relative abundance at this latter site is not unexpected as gorse is one of the main food plants for the well-camouflaged green hairstreak caterpillars.

By the 13th May, the weather had improved considerably and warm southerly winds brought the first red admirals Vanessa atalanta on the 14th, followed on the 16th by the first (at Core Goch Llanllwch 22/361185) of a large scale inyasion of clouded yellows Colia croceus. The first clouded yellows were mostly seen at or near the coast e.g. Carmarthen, Kidwelly and the Llanelli area but subsequently they spread far inland. Such were the numbers in eyidence that local butterfly recorders tired of noting down occurrences - and this year's influx is thought to have easily exceeded the last prodigious "clouded yellow year" - 1983. These spring immigrants bred to produce myriad offspring in the mid-late summer period, for example at Machynys 21/513975 on 6 July, no less than 45 fresh-looking individuals were counted; the progeny of eggs laid on the swathes of lucerne Medicago sativa or other legumes at this locality. There were a few sightings of "pale clouded yellows" - at Banc-y-Lord 22/405047, J.R. Ellis; near Trebersed, Carmarthen 22/390197 on 21 July (Mr & Mrs P. Swire) and near Whitland 22/199166 (Dr Malcolm Holder). It is not sure, however, whether these were the true pale clouded yellow Colias hyale or the pallid variety "helice" of the common clouded yellow. The last clouded yellows were seen (at several localities) in fine autumnal weather on 13 October.

There were a few records (as is usual) of brimstones Gonepteryx rhamni, principally from the SE of the County: at Derwydd 22/613178, 13 April (Matt Ridley); just NW of Trostre 21/522999 17 May; in the Sawdde Gorge 22/790263, 22 May (B. Stewart); N of Fforest 22/58-05, 27 May; near Llangyndeyrn 22/465142, 26 May (A. Lucas); and an autumn record at Betws 22/635117, 27 September (A.L.). One was also watched as it flew along the Glamorgan side of the railway track at Pantyffynnon 22/623103 on 11 April (J. Friese). There was the first absolute confirmation of brimstones breeding in the county when, in early June, Barry Stewart discovered frequent larvae on planted bushes of alder buckthorn Franqula alnus at the Penclacwydd Wildfowl and Wetlands Centre 21/531986; he also remarked that no larvae were found on bushes of purging buckthorn Rhamnus cartharticus at the same site. Spring too saw a dingy skipper Erynnis tages at the small, disused limestone quarry NE of Garn-fawr 22/534150 (on 18 May), and several more a few days later (24/5) on waste ground immediately south of the derelict Morlais Colliery, Llangennech 22/578028. Here, together with common blues, they flew over a rich sward of flowers, including their food-plant, bird's foot trefoil Lotus corniculatus. Some rank grassland alongside the railway line (22/573022) by the colliery had several marbled whites Melanargia galathea on 24 June. A strong colony of marbled whites was present SE of Cefn Gwili 22/583088 (on 17 July), and one was also seen by Pippa Whitton SE of Milo 22/599172 on 16 July; a compact colony was discovered by Jamie Bevan and Dawn Grey by Cennen Tower 22/675214 on the 21st July. An older record has also recently surfaced - another small colony on unimproved grassland near Pant-y-ddeuddwr 22/556116 on 29 June 1989 (David Stevens & Jonathan Turner). The Countryside Council for Wales "Phase I/II Grassland Survey" staff produced a number of useful records during their field work (principally in Dinefwr Borough); these are given below:

Marsh fritillary Euphydryas aurinia

  • Pant-y-bara 22/602179 15 June (1+) - D. Gray & J. Bevan
  • Glyn-deri 22/699141 12 June (1) - D. Gray & J. Bevan
  • N. of Parc Matho 22/443055 22 May (1) - P. Whitton
  • NNW of Llwyn Petris 22/455089 28 May (2) - P. Whitton

Small pearl-bordered fritillary Boloria selene

  • Llwyn-y-bedw 22/736259 25 June ("abundant") D. Gray & J. Bevan
  • Caeau Llwyn-y-cwm 22/641100 23 June ("several") D. Gray & J. Bevan
  • Esgair Tan-lan 22/687475 18 June (one) Graham Motley
  • Bryn Ceiliogau 22/690490 18 June (three) Graham Motley
  • Esgair Hendre 22/671488 25 June (c20) Graham Motley
  • Nant-y-Rhaeadr 22/760426 early July (one) Graham Motley
  • SW of Bryn-gwyn 22/654476 25 June (one) Graham Motley

Many small pearl-bordered were also recorded by the author at Cwm Crychan 22/823390 on 13 June, with individuals flying around the edge of the path which descends obliquely through the bracken to some damp pastures. Julian Friese also noted one by the Usk Reservoir 22/820276 on 14 June, but this individual was just inside the neighbouring vice-county of Breconshire.

In 1991 and again in 1992 an attempt was made to visit some of the sites where marsh fritillaries had been previously recorded, in order to try to assess the true status in the county of this declining species of damp grassland. This survey work was carried out by Nick Thomas in 1991 and Andrew Lucas during 1992; it was not possible to visit all known sites and the monitoring of marsh fritillary colonies will continue.

Marsh fritillaries have been, in recent years, recorded at thirty or so sites in Carmarthenshire, though others undoubtedly await discovery, and about two-thirds of these were visited during the survey. The results revealed some disturbing trends. Marsh fritillaries rely on a delicate balance of grazing and cutting to keep the "rhos" pasture, on which they depend, suitable. At the cessation of grazing the processes of ecological succession cause a site to become dominated by rank species such as purple moor-grass, and eventually to be invaded by scrub; the flower-rich meadow is then lost, and, with it, butterflies such as the marsh fritillary. Approximately 50% of surveyed sites exhibited habitat degradation, particularly parts of Cefn Blaenau (22/580414) and Tir Philip (22/480185).

Low numbers of individuals - less than five - caused by a reduction in the quality of habitat were also noted at Gilfach Wen (22/530429) and Bryn Du (22/478040). When numbers of insects become low, a colony becomes vulnerable to extinction due to chance events, such as poor weather at a critical point in the lifecycle. It is of some concern that a number of colonies seem perilously close to the edge. One colony at Cae Cwm Tywyll (22/481239) is thought to be extinct, and it seems inevitable that other losses will be confirmed in the future.

On a more positive note it is still possible to see thriving colonies in the Llanelli area particularly at Waun Wyllt (22/498055), Cwm Morlais uchaf (22/525095) and also Cencoed Uchaf (22/482032) where approximately twenty individuals were on the wing on a sunny afternoon in June 1992. It should be noted however, that even the latter site is declining in quality due to scrub invasion, a fact which highlights the need for sensitive management to conserve the marsh fritillary in its Carmarthenshire strongholds.

Dawn Gray and Jamie Bevan recorded graylings Hipparchia semele at Rhiw-ddu 22/725208 (20 Aug) and SE of Capel Tydist 22/675235 (19/8), whilst Graham Motley reported a very large population on old mine workings at Nantybai 22/777446 on 26 July. He also recorded this species at two other sites - one on a Molinia/Calluna wet heath NE of Cwm Seethe 22/773443 (15 July) and two by Llyn Brianne Reservoir 22/794486 (29 July). In Carmarthenshire, most grayling colonies are on the coast - amongst the extensive dune systems or on urban wasteground. It also occurs on some of the dry and rocky sparsely-vegetated uplands - around the coalfield valleys, on the Millstone Grit ridge, the Mynydd Du massif and the upland block of the extreme NE (see Fig. 1). Its predilection for stone-strewn arid habitats is reflected in its Welsh name "Iar Fach y Graig" - "the butterfly of the rock".

There was only one 1992 record of the dark green fritillary Argynnis aglaja at Allt Rhyd-y-Groes 22/765485 on 25 June - whilst four silver-washed fritillaries Argynnis paphia (and purple hairstreaks Quercusia quercus) were reported by Julian Friese from the afore-mentioned Cwm Crychan in August. Another was reported at Gelli Aur 22/598198 at the end of July by wardening staff. The arboreal purple hairstreak was additionally observed by Graham Motley at Rhandirmwyn 22/783424 (16/7) and near Llansawel 22/610364 (Aug). Julian Friese saw a white-letter hairstreak Strymondia w-album at a known site - Coed Penrhiwiau 22/659237 near Bethlehem, and Malcolm Holder reported a "new" locality where this elusive butterfly was known to at least 1989 - an old wych elm near Whitland Abbey 22/209181.

Figure 1: The known distribution of the grayling Hipparchia semele in Carmarthenshire