SOME DISCOVERIES AND SOME TENTATIVE SPECULATIONS ON GREEN HAIRSTREAK VARIETIES IN WEST YORKSHIRE AND ITS BORDERS
                   
Caecus


Ab: caecus on bilberry on a steep hillside above the river Ryburn opposite Kebroyd near Ripponden, West Yorks. This big colony of Green Hairstreaks can be approached following the route of a hidden but remarkable disused railway (Surrealist-like in its brooding and foreboding, rocky. dark splendour) between Halifax and Littleborough, West Yorks. Photographed late on a hot afternoon, Thursday, May 29th 1997.
 
Punctata


Ab: punctata Green Hairstreak perching on the lower branch of a small oak tree at Caley Deer Park where the Chevin Forest gradually thins out into Caley Crags towards Poole in Whardedale, West Yorks, Friday, June 3rd 1997 on what was a scorching hot day.
 

PLUS AN APPEAL FOR MORE INFORMATION

    It has been suggested until recently that Green Hairstreaks are virtually absent from VC 63. In short, the area of Yorkshire comprising the industrial/urban belt of the West Riding up to the Lancs' border and parts of South Yorkshire down to Derbyshire. S L Sutton and H E Beaumont in their excellent book: "Butterflies and Moths of Yorkshire" (NYU 1989) subscribed to this view too. Up to that date, the Green Hairstreak in VC 63 and roughly its borders with VC 64 was, more or less, confined to a small, steeply sloping bank near the White House on Otley Chevin.

     We now know, after a more intensive search throughout the 90s, this is wide of the mark. Not only is the Green Hairstreak present on many parts of the Chevin (Caley Crags, Shawfield, a coppice in Stag Wood, Miller Lane and the approach to Surprise View) but can be found on any sizeable bilberry/heather clump on the slopes of the Pennines favourably situated vis-a-vis sunlight, some shelter from the tenacious upland winds and also, where the particular red ant, which it seems to need are in good numbers. (In parenthesis, the minutiae of this Hairstreaks' relationship with the ant has never been fully investigated). More astonishing perhaps, the butterfly can be found - usually in small numbers - in locations which do not fit such criteria and are, quite frankly, very bleak.

    In saying this, we do not wish to impugn the seeming inadequacies of past observers and recorders. Most likely, these Lepidopterists were more or less right, given the previous, much cooler, weather conditions. We must also remember entomological research has always been extremely thin on the ground in industrial West and South Yorkshire. These areas were and are, unexplored. The frightening phenomenon of recent global warming, paradoxically, has meant that many species have dramatically extended their range in the Pennines. Populations of fragile invertebrae - at the extreme limits of their range - have mushroomed.

    This, it seems, is particularly true of the Green Hairstreak and some odd and interesting variations seem to have been thrown up by it too.

   Firstly, this big but dispersed Green Hairstreak population raises a general question which can probably only be answered speculatively. Is it the remnant of a vast relic population going back millennia or, is it of more recent origin?

     Much depends on how we define relic. It tends to refer to the flora and fauna of places like the Scilly Isles which once were connected by a land bridge to the Iberian peninsula prior to the rise in sea levels marking the ending of the last Ice Age. We must remember that most of the Pennines, 5,000 years ago, were wooded when more settled agricultural communities began to replace hunter-gatherers and which, in duration, easily outweighs by tens of thousands of years, the subsequent history of humanity. Originally, the areas of open upland were very small indeed and the interaction of man and nature probably led to a considerable increase, over time, in bio-diversity. Upland areas would have been slowly cleared of trees and the marshy valley bottoms felled and drained in a rudimentary way. Extensive monastic settlements led to large-scale land clearances and the criss-crossing of huge clerical demesnes with dry stone walling for sheep grazing. With the dissolution of the Monasteries, land passed to Court favourites and there was a rise in small-scale agriculture, particularly sheep folds. (Street names still bear testimony to this more diverse mode of production - e.g. Suddard's Fold and Knight's Fold etc, in urban Bradford). Finally, the increased demand for iron put an end to what was left of the original wildwood when charcoal was needed for smelting iron ore. One can but assume that heather and bilberry began to quickly grow on the exposed, peaty, alkaline soils.

     However, we must remember also that extensive sheep grazing limited the spread of bilberry, the Green Hairstreaks food plant in most of the north. Herds of goats were, furthermore, kept for essential rough cropping and milk. Overlaying the bank sides of Shibden Head, Bradford 13 (the caecus form of the Green Hairstreak was discovered here in 1999) and where the bilberry grows in profusion, are intersecting, low, dry stone walls still blackened with the soot of the industrial revolution - silent witness to a past era of intensive sheep pasturage. (There is even the stone remains of a circular shepherd's hut with a primitive hearth). Much of this land must have fallen into disuse over 100 years ago with the great agricultural depression of the late 19th century when vast economies of scale meant it was cheaper to import wool from Australia, New Zealand and Canada. In the name of anti free-trade liberalism, supra-national appeals to the myth of Empire loyalism hid from view the ruin of thousands of small farmers in upland districts of Britain. In Elizabethan times, in the words of Thomas More, "sheep ate men". But now it was the turn of the Green Hairstreak to benefit: bilberry began to encroach on land taken out of production by the system of Imperial Preference.

    There is yet another (unassailable) fact. For some 300 years prior to 1700/1750, Northern Europe was in the grip of what is now termed the Little Ice Age. Briefly, a reduction in salinity caused the Gulf Stream to cool. It coincided with peasant revolts across Northern Europe and the English Civil War. The Thames frequently froze over. The social upheavals must have been accompanied by un-remarked changes within natural populations. We can, we think, divine this from the increased importance given to co-operative, large-scale farming methods, winter fodder and the deliberate introduction of new, possibly hardier, plant species which could be farmed. Such species are given prominence in the writings and practises of the Digger, Gerard Winstanley. Almost certainly, the Pennines and the surrounding lower slopes, must have been far colder than they are now and the invertebrate population much reduced. In all probability it was just too cold for the Green Hairstreak. Sadly, we are doomed to remain within the realm of speculation although studies of the Green Hairstreak in Alpine situations might be helpful here. The infuriating near absence of a fossil record amongst soft-bodied invertebrates means we have no way of checking. Probably it is a major reason why Entomologists held out for so long against Natural Selection; (if we are to believe D E Allen's assertion in "The Naturalist in Britain").

     However, it's our contention (and obviously we could be quite wrong about this), that the big Green Hairstreak, Pennine population, is probably no more than 300 years old and it's wide range is far more recent, possibly no more than a 100 years old. As far as numbers are concerned, perhaps we could suggest something less than 20 years marking the big increase in density and concomitant with the greenhouse effect.

    Obviously, both today and in yester-year there's been little monitoring of butterfly populations in Yorkshire. Moreover, the Green Hairstreak is, in any case, an elusive and well-camouflaged creature which, together with possibly low population numbers in the past, perhaps escaped detection. Only regular, quite painstaking monitoring on likely sites would have revealed them and that wasn't forthcoming. Suddenly, global warming has made the Green Hairstreaks' profile inescapable. They seem to be everywhere: perching on favourite small birch and oak trees among bilberry-covered hillsides; alighting briefly on blackened Yorkshire stone walls; wandering off into the alien territory of hay meadows where farm animals graze; flying between patches sometimes half a kilometre apart etc, etc. Always, always, under the hot sun, restlessly on the move.

    Perhaps too, the butterflies quickly fan outwards from a strong core population ably assisted by the thermal winds which abound in the Dales and which often appear strongest just as one descends from an upland plateau or hill top, and at a slightly higher altitude than the bilberry. Much observation has been made of the peculiar perching habits of the Green Hairstreak on the branches of small trees and, now and then, darting out from their habitual branches chasing away invading males. Often then, in some kind of dizzy roller-coaster, they tumble about each other shooting high up into the blue yonder to be lost from sight. Suppose females are chased in this way too and then get caught up in the strong thermals to be blown far and wide? One or two butterflies will fall back to earth far away, occasionally landing on the ubiquitous green bilberry sward. However, in saying this, we've never been able to distinguish male from female in this sudden, dance like ritual simply because it takes place in flight.

   Green Hairstreak varieties may give such hypothesis an added credence. West Yorkshire seems to be undeniably rich in the two major varieties of this butterfly: the punctata form (with white spots on the underside of the upper wing) and, the caecus form (with only one spot often a little larger than the normal spot - on the underside of the lower wings). Geographically though, they do seem to reside in two distinct areas and are - if you like - split by Bradford city. To the north and north west resides the punctata (the predominant variety all over the Chevin) and to the south west resides the caecus, stretching from Shibden Head, Bradford 13, across to the Ryburn valley virtually to the river's source close to the M62. there seems to be no reason why the caecus shouldn't extend much further in a south westerly direction crossing the Yorks/Lancs border near Oldham and even towards the Derbyshire Dales. Equally, does var punctata make an appearance on Almscliff Crag and in the Nidderdale populations? We would be pleased to receive communication on this matter.

   Perhaps the prevailing winds have played a major part in the distribution of var: caecus as the colonies so far discovered, all follow through from a south-westerly direction towards Oldham where there are many bilberry-covered hillsides just off the M 62. In 1997, we photographed a huge Green Hairstreak colony near Ripponden in the Ryburn valley. Over 6O% of the photographs turned out to be var: caecus. It was quite a surprise.

   Having given what amounts to an upbeat assessment so far, a strong word of caution is now needed. The Green Hairstreak seems to be quite a delicate butterfly. It is an ardent sun lover never venturing out even in slightly dull conditions and which in poor spring weather could have an adverse effect on population numbers. What's more important, is it particular susceptibility to heavy rain especially as an imago. The young larvae too are almost equally vulnerable when, aided by moisture, disease can spread. (C/f "Ecology and Conservation of Butterflies" A.Pullen. Chapman and Hall 1995).

    Are we now beginning to experience the downside of global warming as we head into a period of very unpredictable weather conditions: sudden floods out of season; increased general precipitation; possibly more cloud cover in more humid conditions punctuated by extreme dives in temperature (e.g. 7c was recorded on June 2nd 1998 at Leeming, N Yorks ).

     After having lived throughout the 1990s in probably unprecedented climatic luxury, the Green Hairstreak - we would suggest - has been quite badly damaged by the odder climatic behaviour of the last 18 months or so. Perhaps there's been as much as a 90% population crash on the West Yorks Pennines after two extremely wet and overcast springs in 1998 and '99. Recovery however, can be very quick given favourable circumstances. Generally, it's probably true to say that climatic conditions plays the predominant role in the rise and fall of butterfly and moth populations in the Pennines and always has. Land reclamation for farming (apart from centuries past) pesticide use and a dispersed modern urbanism (now greatly exacerbated by the collapse of the nuclear family and subsequent singles living) plays little part in butterfly survival here and, quite unlike the south east of England, where many a Green Hairstreak colony has been wiped out by such contemporary factors.

Take some observations from one 'new' site: Shibden Head, Bradford 13. Late May/early June 1998.

     Days and days spent on Shibden Head at the top of Shibden Dale in persistent cold and cloudy weather revealed no Green Hairstreaks in a location which is a veritable sun trap and where Holly groves exist in plenty (the Holly is a tree which, ironically, hates frost). Occasional very fitful bursts of sun revealed a Holly Blue or two (how long have they been there?) but no Green Hairstreaks. Although we tried beating small oaks, birches and the thick bilberry, it was all to no avail. David Blakeley (VC 64 Butterfly Recorder ) has since informed us that this old technique won't work as the butterflies are in such a state of extreme torpor that they need about 45 minutes of indirect heat from the suns rays before stirring. Moreover, the Yorkshire Green Hairstreaks roost very low down around the roots of bilberry close to the soil. This is in marked contrast to their southern cousins which often roost on the branch of small hawthorns among the fresh green leaves, or even on the bole of the tree itself usually 12 centimetres or more from the ground.

   Then came the freak thunderstorm of June 2nd 1999. Shaking our heads, we reckoned the deluge must have been all too much for these small green butterflies on this site and the adjacent Ryburn valley. Sure enough, as the next few days were to prove, all that remained were the tattered remnants of what, two years previously, had been a horde.

   Saturday the 5th of June was sunny on Shibden Head. After the storm, a depleted population of Latticed Heath and Carpet moths wearily flew but, yet again, not a Green Hairstreak in sight. Only by applying gentle beating motions across the bilberry tops on this sunny day, were Green Hairstreaks flushed out. Their flight had no power and - so unlike these sprightly insects. We felt that the lack of sunlight over the previous three weeks had not only induced on-going torpor but starvation too. Had the butterflies possibly become too weak to even nectar' Exclusively here, the nectar source is bilberry and if the florets are damaged (as they appeared to have been by the storm) just what do the butterflies do to replenish themselves?

   Interestingly, the few weakened survivors belonged to var: caecus. On the same day too, the only Green Hairstreak we saw on the wing on the Ripponden site about 9 kilometres from Shibden Head, was a caecus too. Maybe all this was purely fortuitous. On the other hand, does the caecus form bestow some kind of survival value in this part of the Pennines?

    There is one further point that is not connected with the weather but does relate to the dominant Green Hairstreak varieties. The resemblance of the resting Green Hairstreak to bilberry leaves is very striking affording far grater protection than the leaves of hawthorn, oak, birch and sycamore which are favoured as perches. Could not the markings which distinguish the caecus and punctata varieties reflect the rust markings to be found on bilberry, thus making the butterflies even more inconspicuous particularly during the crucial egg laying period? At a cursory glance, the bilberry on the Chevin appeared to be more spotted during the Green Hairstreak emergence than the greener relatively un-mottled bilberry found at Shibden Head for example. (Remember, on the former site, the multi-spotted punctata flies, while on the latter, it is the one-spot caecus. Rather than being an example of random genetic drift, which could be of some survival value later, the punctata and caecus dotting may already confer a crucial selective advantage. Those supreme mimics of the insect world, the Bush Crickets (the Katydids) and Leaf Insects (the Phasrnida) copy fungal spots as well as leaf crumpling and venation which, of course, the less perfect mimicry of the Green Hairstreak does not. Also, we may find that in the case of the punctata and caecus, we are dealing with a predominantly female sex-linked inheritance. The African Swallowtail, (papilio dardanus) famously mimics several distasteful species of butterfly. The mimicry is however restricted to the females. This sex controlled inheritance is thought to arise partially from the increased vulnerability of the egg-laying females. The same could apply to the Green Hairstreak varieties with the obvious proviso that it is cryptic colouring that provides the protection here and not Batesian mimicry of a poisonous model. Much work obviously remains to be done.

    Finally, who can authoritively say that this question may not turn out to be an example of the on-going debate between geneticists and natural selectionists? In the 1930s, J B S Haldane had come to the conclusion that "innumerable characters show no sign of possessing selective value" and were only important for classification purposes. As a result of painstaking observation, it was found that many seemingly random characteristics did serve a previously overlooked purpose. The overall dun-coloured female scotica form - lacking eye spots - of the Large Heath was found to be perfectly adapted to a life, largely passed low down amongst browning vegetation, where eye spots would have been an invitation to predation. And, let us remind ourselves of the opinion of the great Alfred Russell Wallace who insisted that persistent traits had some "selective advantage" even if not immediately obvious. Wallace, it must be said, was a very keen observer and interpreter of the insect world - far more so than the unromantic Darwin who was curiously beguiled by the beauty of butterflies and, whose attitude to them on the voyage of the Beagle was more rhapsodic than analytical.

    But to return to the more mundane subject in hand. Seeing the var caecus abounds in the best years in the area of West Yorkshire outlined here, could we find the illusive variety which has no spots at all? E B Ford reckoned that every caecus contained some kind of spot (and which is our experience). However, Richard Lewington in "The Butterflies of Britain and Ireland " (NT. Dorling Kindersley 1991) illustrates a caecus with no spots. In the intervening decades between the two books, has a caecus without spots been discovered? It seems a few trips to the library of the Linnean Society would be in order here.

    And.... to speculate further. Is there an actual geographical dividing line in these Dales between the punctata and caecus form? An area of bilberry perhaps between Bradford 13 and say, Haworth (Denholme or Thornton perhaps') where both varieties converge or, where possibly, a "new" sub variety, combining both variations, exists? Or is this just tantalising whimsy?

   We have looked closely at and photographed Green Hairstreaks in southern England on the North Downs (especially Banstead Downs). Never have we come across caecus, punctata or indeed, any other variety. However, the Autumn 1999 issue of "Butterfly Conservation News" does contain a photograph of what must surely be a var: caecus in an article on Essex butterflies. Our experience has been that the Green Hairstreak is very difficult to find in south Essex where the photograph was purportedly taken. Generally though, are Green Hairstreak varieties more a northern than southern phenomenon? More precisely, do caecus and punctata abound in the bilberry-rich, micro-climate on the North Yorks moors? Do the populations on Spurn, Sunk Island sands or, Cherry Cob sands and where the larvae feed on gorse or broom, exhibit varieties?

    Further afield, do the vast Scottish or Cornish populations, helped along by the milder effects of the Gulf Stream, contain considerable numbers of varieties? It would he interesting to come up with some comparisons.

WE WOULD BE GRATEFUL FOR ANY INFORMATION ON THIS SUBJECT.

PLEASE WRITE TO: DAVID AND STUART WISE:

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