In Pursuit of Butterflies

by Matthew Oates

  May behaved itself, for once. There were no frosts, gales, deluges, floodings or other ghastlinesses so characteristic of modern Mays. That meant that spring butterflies were not blasted away prematurely, for once. At the end of the month a hand-picked gang, organised by Dr Dan Hoare of Butterfly Conservation, spent two fine days surveying the northern half of the MOD's vast woodland and downland complex at Porton Down for the Duke of Burgundy. Over the two days 256 Burgundies were counted there, a huge tally by modern standards, indicative of a nationally important site. Unusually, many of them were seen well away from any visible Cowslips or Primroses, the larval foodplants. I myself found twelve male territories nowhere near any obvious Primula patches. Although our butterflies behave, and perform, differently in the few large sites which still offer them landscape-scale mobility, this was distinctly odd, and worrying. The diary concluded: I'm not sure why the butterfly is still thriving at Porton and suspect it could suddenly crash. A delightful colony of Pearl-bordered Fritillary was flying along the edge of Towerhill Plantation there, breeding in violet-filled glades where young Beech trees had died off prematurely, through what foresters call crop fail. Four Small Pearl-bordered Fritillaries were also seen, the first recorded at Porton for some twenty years. There are remarkably few records of this butterfly breeding on chalk downland, though it breeds freely on Carboniferous Limestone.

  And the Marsh Fritillary exploded wondrously at Strawberry Banks, producing the best adult counts in twenty years of close monitoring. I counted 557 in 45 minutes over the 4-hectare site. The males were jostling for position on buttercup flowers and chasing each other about merrily all along the valley bottom. Some dispersed, and were seen as far away as Stroud. The females, though, had been driven away from the breeding grounds on the lower slopes by the over-amorous males and were sulking high up on the upper slopes, well away from their foodplants. At some point they would have to sneak back down slope to lay their eggs.

  Then, over in Savernake Forest, at the end of the month, Keats ascended. He had been found as a caterpillar the previous September, when less than a centimetre long, and was now full-grown and turning pale at the feet – a sure sign of a Purple Emperor caterpillar ready to pupate. I watched him ascend from his feeding bough about 2.5 metres above ground to the top of the 10-metre sallow that had been his home for the last ten months. He disappeared into the upper canopy and was seen no more. The journey took all of seven minutes, during which time I recited Shelley's ‘Adonais’ for this most illustrious of caterpillars. It ends:

  The soul of Adonais, like a star

  Beacons from the abode where the Eternal are.

  Keats was arguably the greatest caterpillar ever to walk this earth. Later, I searched in vain for his pupa, spending 45 minutes scanning every spray through binoculars, lying on the ground to obviate back and neck ache. A dog woman passed by, silently.

  June produced its worst on its first day. Then, having got that over and done with, came good, delivering a superb second half. A very good butterfly year was steadily materialising, 2010 was battling its way to greatness. At Collard Hill, the Large Blue started to emerge on the 6th. Soon it became apparent that this royal-blue butterfly was set for a bumper year there. Habitat conditions were spot on, following precision grazing management, a goodly number of eggs had been laid the previous June, and the weather was set fair. The weather got a bit too fair, as the sward began to show signs of drought, which can be disastrous for the ants on which this most fastidious of butterflies depends. It was the visiting butterfly photographers who really suffered, though, for this steep slope reflects heat intensely. On hot midsummer days the males would become active after 8 am, to fly along the slope bottom for an hour or two in the hope that virgin females in need of their services would tumble down to seek them. Then, as the day heated up they would fly up to the upper slope, and patrol there, taking advantage of some vestige of a cooling breeze. When that got too hot, they would take an afternoon siesta, becoming active again as the day started to cool down.

  Even the Black Hairstreak, one of my bogey butterflies, produced one of its occasional years of plenty. A visit to the meadows and hedges around Finemere Wood in north Buckinghamshire, with Dennis Dell, produced a tally of 46 individuals. That is as prolific as I have ever seen this butterfly. Luck was with us, as the day was dead calm, which meant that the butterfly could flit merrily along Blackthorn hedges that are too exposed in any noticeable breeze. It is perhaps its own worst enemy here, detesting wind but inhabiting exposed hedgerows – probably because it has largely been ousted from its preferred sheltered woodland haunts.

  In some of the combes radiating off Dunkery Beacon, on Exmoor, the Heath Fritillary resurged wonderfully, due to a combination of good weather and successful habitat management work. The colony at Bin Combe put on a stunning show. Tick numbers seemed to be well down as a result of the cold winter – I found only five on me. At Halse Combe, on the edge of Porlock, experimental management enabled the butterfly to recolonise one of its strongholds. I even saw a female laying a batch of eggs, the first time I think anyone has seen this approachable and unwary butterfly laying eggs on Exmoor. Normally, the females must lay amongst the Bracken, out of sight. This particular female was spotted fluttering with dithering wings along Grannies’ Ride, the bulldozed track that runs along a contour line halfway up the steep south-facing slope of Halse Combe. I knew that flight, it was of a female intent on laying eggs. She was spying out warm hollows in the bankside vegetation.

  Diary, June 15th 2010: Eventually she settled in one such Aladdin's cave, overhung by gorse, Honeysuckle, low Bracken and Bell Heather, and was clearly laying, deep in amongst dead litter. It was hard to see what she was laying on but no Common Cow-wheat [the larval foodplant] was evident there.

  I returned at 6 pm to analyse the laying site and do a detailed vegetation quadrat, only to find that the footpaths gang had been along during the afternoon and strimmed the entire breeding area. Sometimes the Fates are cruel.

  Late in the month the last of my Savernake Purple Emperor larvae, Ted Hughes, went off to pupate and in doing so revealed itself to be … female. Yes, Ted Hughes had transmogrified into Sylvia Plath. The folly of my naming caterpillars after great poets of the English language was finally rammed home.

  In the Sussex woods, the White Admirals and Silver-washed Fritillaries were appearing in numbers, and were promising great things. I saw two totally black ‘Black Admirals’, the rare ab. nigrina form of the White Admiral, in Madgeland Wood. There followed an excellent night at Knepp Castle, where dinner consisted of eel cutlets, partridge and guinea-fowl breasts with asparagus, a definitive gooseberry tart, a serious cheese board and three different wines. Keats's ‘endless fountain of immortal drink’ was spouting rampantly.

  Diary, June 24th 2010: As a result I broke out of my garret bedroom, at 1.30 am, and rampaged on the castle battlements under a trenchant full moon, in the manner of Percy Bysshe Shelley and Lord Byron at the Villa Diodati. Too much coffee probably. Hornets were batting about. The only thing missing was a loose woman.

  The following day the eyesight was playing up and I misidentified a butterfly. The first Purple Emperor of the year was seen that day, at Bookham Common, Surrey, by Ken Willmott – after a vigil of three consecutive days. I may have seen one earlier that morning, at a distance, in Madgeland Wood, near Knepp, but for some reason the eyes were not focusing properly. The summer of 2010 was becoming glorious.

  Fermyn Woods were calling, up in Northamptonshire. This is BB's heartland, and these are his Emperors – ‘my Emperors,’ he used to call them, believing he had re-established the species there through breeding Emperors in his garden. Certainly he helped them, but it is likely that the butterfly had never died out in Rockingham Forest. Whatever, it is vital to be in Fermyn for Big Bang day, which sees the main emergence of Purple Emperor males. Big Bang day actually lasts for two or three days. In 2010 it took place on July 3rd to 5th, after the butterfly had started
to emerge there on June 30th. Staying in Sudborough Green Lodge cottages again, by courtesy of Fermyn Woods Contemporary Art, I knew there was deep magic in the air early on July 4th, the sort of magic in which BB believed. Sure enough:

  Diary, July 4th 2010: At 11.45 I spotted a pristine Purple Emperor male ab. lugenda flying low down the ride some 60 metres distant, in dappled shade. I recognised him as a dark variation instantly. Incredibly, I had the ride to myself at the time – for the Gods choose their moments carefully. This butterfly was one of the wariest Emperors I've encountered. He favoured dappled shade, as do ‘Black Admirals’ and valezina females of the Silver-washed Fritillary, as did last year's lugenda in Alice Holt. But he never settled for more than a minute, not finding much to his royal liking, and he led me a merry dance along half a mile of ride. I lost him at one point, but he returned three minutes later to the favoured stretch below the oaks just north of Neil's Corner. Eventually he flew off north, and I lost him as he flew away over dense sallow scrub. I lost a few pounds in weight in pursuit of this miraculous insect.

  He was very similar to last year's Straits lugenda, though a little darker, with fractionally less white (two and a half white spots in the forewing only, and not a vestige of any other whiteness, at any angle). Until one has seen the true purple of lugenda (formerly iole) shimmering in low flight through the dappled shade of the July oaks One Has Not Lived. All told, I reckon I saw about forty male iris today, all pristine or nearly so. No females, again, though they must be starting to emerge.

  Entomological lightning can indeed strike twice in successive years, but only with the Purple Emperor.

  But it was the White Admirals and Silver-washed Fritillaries that really stole the show in July 2010. The old collectors would have loved this year, for camilla and paphia, as they knew these two forest giants, varied strongly. My personal tally was ten ‘Black Admirals’, three or four of which were probably the rare all-black ab. nigrina, the others the less rare semi-black ab. obliterae. This haul took my lifetime's tally of ‘Black Admirals’ into three figures. Paphia also produced a scatter of black aberrations, called ab. confluens and ab. ocellata, and a fair few females of the valezina colour form. Both these two species emerged in excellent numbers in many southern woods, and Silver-washed Fritillary was seen in many new localities, outside its known range. Butterfly of the year was a toss-up between these two and the Purple Emperor, though the White-letter Hairstreak also needs mentioning in dispatches, for making one of its periodic come-back tours.

  Lightning also struck twice in that St Swithun, for the second year running, brought an autumnal gale, a worse one which lasted for 48 hours. Again, Purple Emperors and the Purple and White-letter hairstreaks were decimated in the modern sense of the term, in sensu hodie. The day after the storm I visited Oversley Wood, a Forestry Commission wood near Alcester in Warwickshire. The Purple Emperor had been introduced here eight years previously, and was thriving. A spectacular emergence took place in 2010, with no fewer than eighteen individuals being seen at the start of the Oversley flight season on June 28th. I watched a courting pair.

  Diary, July 16th 2010: At 2.10 a nice-looking female flew high along the ride and was intercepted by the resident male. A promising courtship flight instantly commenced, lasting three minutes before they nearly joined on a high Scots Pine spray. However, the minx suddenly changed her mind and dropped to the ground, in rejection mode, before ascending to the sallows and vanishing, leaving the poor male chasing pheromone scent in the air. Ladies, you can behave better than that. During this courtship my colleagues were led astray by a loud shout of ‘Camberwell Beauty!’ from down the ride. This I chose to ignore, and rightly so, for it proved to be a phantom.

  The diary continues: I must congratulate Derek Smith, who bred and released Purple Emperors here, on his fantastic judgement of habitat suitability and sallow quality. Butterfly breeders are often castigated for their activities, and their expertise is seldom recognised or accepted, but Derek has done a superb job in establishing this lovely butterfly here, and in some other Warwickshire woods where it has thrived and spread.

  Weather-wise, July 2010 saw a north-west/south-east split, with dry and sometimes hot weather dominating the south-east, whilst the north and west became increasingly cloudy and wet. Gradually the sun sank on the whole summer. August was decidedly poor, especially in the west where the holiday season was spoilt by rain. When the sun shone, butterflies were actually in good numbers, but their opportunities steadily diminished. On August 22nd I arrived at the entrance to Calstone Coombes, an unknown land of secret downland combes near Calne in north Wiltshire, and was welcomed by a stunning display of Adonis Blue males seeking moisture from mud down-slope of an overflowing cattle trough. This was an amazing, tropical-like experience. A cloud of azure butterflies rose before me. It was not of this earth. However, a wet end to August effectively wrote off the summer brood of the Adonis Blue. The late summer weather was so poor that the Clouded Yellow did not bother to cross the Channel. Maybe they sensed that September was going to be poor.

  It was poor, and in consequence the butterfly season fizzled out early. I spent much of the autumn searching for Purple Emperor larvae in Savernake Forest, conducting standardised searches, repeating the previous autumn's work. The final tally was 66, down from 141. Presumably many females had been killed off by the St Swithun's night gale, resulting in a greatly reduced egg lay. The autumn was intermittently very wet, but with a scatter of glorious autumn days wherein Savernake shone. Then, quite suddenly, on November 19th conditions became intensely cold, with the leaves still on the Beech and oak trees. These leaves were bleached by the bitter weather; lifeless and colourless, they remained frozen to the trees, unable to drop. Snow fell at the end of November extensively in the north and east, and the coldest December on record in the UK ensued. Snowfalls occurred throughout much of the UK on the 1st and 2nd, the north and east became snowbound, the M25 gridlocked itself spectacularly and Gatwick airport closed down for three days. Starving birds flocked into gardens. A short mild spell provided some respite before a nationwide ten-day freeze-up commenced, which included a bitter White Christmas. The year ended spectacularly.

  The new year was borne in on a calm, grey and mild night, with moths fluttering at the study window. Purple Hairstreak eggs were hard to find. The adults had been clobbered by the St Swithun's gale of 2010. Conversely, White-letter Hairstreak eggs were relatively plentiful, perhaps because this butterfly lays its eggs a little earlier in the year than its cousin and so had managed to lay the bulk of them before the gale hit. Down in Savernake, the snow and frost had protected hibernating Purple Emperor larvae, and not a single loss was incurred during December. Best of all, Mrs O found an Orange-tip pupa on a dead Garlic Mustard head. Orange-tip larvae almost invariably wander off their Garlic Mustard plants prior to pupating, so pupae are rarely found. This pupa was extra special in that it was completely black. Sadly, it vanished in late February.

  Despite the cold December some Marsh Fritillary larvae emerged from hibernation at Strawberry Banks on January 19th, ten days earlier than normal. By early February they were coming out en masse. Soon it became apparent that a record number of larval webs were present. An absolute count of webs over the 4 hectares in mid-March reached a dizzy total of 340 webs, each containing an average of 75 larvae. That worked out at some 25,000 larvae in total, only a tiny percentage of which appeared to be parasitised. Numbers were also remarkably high at Hod Hill and on Fontmell Down in Dorset. It looked as if the Marsh Fritillary was going to take over the world, especially as winter petered out early and gave way to a sublime March, which in turn led into the warmest April on record, and one of the driest.

  The only problem for the Marsh Fritillary was that its larval foodplant, Devil's-bit Scabious, had not grown at all in the early spring drought. Normally the emerging caterpillars make do with the previous year's leaves for a while before homing in on the fresh growth, but this time it was different
: the bitter December had withered the previous year's leaves into the botanical equivalent of slivers of old leather, whilst the drought prevented fresh growth. The spiny black caterpillars carried on regardless. By early April they had eaten virtually all vestige of Devil's-bit Scabious on the Banks, old leather, stalks and all. Twenty-five thousand larvae over a maximum of 2 hectares of turf in which the foodplant grew proved to be an unrealistic stocking rate, especially in a drought. They ate themselves out of house and home, and then broke out. They invaded the adjoining Three Groves Wood, an ancient Beech wood, where they consumed Honeysuckle leaves, which Marsh Fritillary larvae will eat in captivity. They dispersed far and wide. I found one down the path 255 metres into the wood. Better still, they crossed the stream that gushes along the valley bottom, somehow. One was found up by Oakridge church, half a kilometre up a steep slope! Many died, either of starvation or from being trampled on whilst warming up along the footpaths. I found 22 squashed larvae along one 100-metre stretch of path, suggesting that far more were squashed by walkers than were parasitised.

  Later, I found the pupae, the butterfly equivalent of a Yellowhammer's egg – pale, with curious and rather random black squiggles, and surprisingly cryptic amongst dead grass. They were not in grass tussocks, where I had expected them to be, but right out in the open, in sparse short turf. If the fine weather held the butterfly would abound, and take over the whole royal county of Gloucestershire. If ...

  By the end of a remarkable April I had seen 27 species of butterfly, beating my previous personal end-of-April record of 23 in 2007. With a little more effort I could have seen 30 species, half the UK fauna. As it was, April 2011 produced my earliest ever Duke of Burgundy (on the 9th), Adonis Blue (30th), Brown Argus (24th), Common Blue (26th), Small Blue (24th), Marsh Fritillary (26th) and Small Pearl-bordered Fritillary (20th). More relevant, 2011 went on to claim the earliest UK sightings for a number of species, despite the fact that the fine weather ended during May.