Neil Hulme

[Roger Gibbons]

I find this a fascinating thread/diary, especially when it relates to Long-tailed Blue, an intriguing species from many perspectives. It’s a great read and very informative, so thank you Neil for posting in such detail. It is a species whose ecology generates so many questions, some of which I raised in a BC Zoom talk on butterfly behaviour earlier this year.

Its distribution globally is exceptionally wide – across Europe, Africa, parts of Asia, Australia (where most species do not resemble anything European) and even Hawaii. So did it exist in its present form at the time of the break-up of Pangaea, or is it the result of migration over many millennia?

It is highly migratory when most other species of Blues are rather sedentary – why should it be different, and what makes the difference?

Why is it reaching England when its distribution in France is largely limited to the lower third of the country? What is prompting the migration as it does not appear to be a mass emergence causing migration or dispersal? It doesn’t appear to be a few wind-assisted individuals blown off course.

The larval hostplants used are quite wide when most other Blues are quite fussy.

There’s a PhD study for someone….

Also, the underside pattern is quite variable but generally following the same outline. The recent one that was presumed to have just emerged is quite plain compared to the norm. The ones I see in southern France are all reasonably similar to the normal pattern but one I saw in the Pyrenees in 2019 had a pattern that almost induced nausea.

Roger

[Neil Hulme]

Thanks, David. The action continues during even the shortest spells of sunshine. I'm spending a lot of time in a Bognor garden at the moment, where some of the complexities of this species' behaviour are becoming ever clearer.

Thanks for your interest, Roger. This is a fascinating and most impressive species. Some of your questions are addressed in the following text, which is the entire species account I wrote for The Butterflies of Sussex (2017). A lot of the ideas I proposed back then have really firmed-up now, based on observations since 2015. For instance, I'm now certain that a return migration occurs; the species is behaving very much like the Painted Lady.

BWs, Neil

Long-tailed Blue (Lampides boeticus)

In recent years the Long-tailed Blue has provided the Sussex butterfly enthusiast with some of the most exciting times in the entire history of the county’s Lepidoptera, most notably the annus mirabilis of 2013. This account also draws on the second of two unprecedented influxes of this previously very rare immigrant, during the post-atlas survey year of 2015. The opportunity to include such significant data could not be overlooked.

This is one of the world’s more widespread and successful species, being distributed across Africa, southern Asia and Australia. In Europe it is only permanently resident along the Mediterranean belt. It is a highly adapted and enthusiastic traveller, with a well documented ability to cross seas and mountain ranges. The Long-tailed Blue is capable of both high speed and endurance.

Each summer it migrates northwards into more temperate parts of Europe, but historically has only rarely penetrated as far north as the South of England, at least in any numbers. Previously, only 1945 and 1990 have seen incursions of any significance, but the summer of 2013 was to break that mould, and the re-run in 2015 seems to suggest that a new era has been ushered in.

The general consensus remains that it is as yet unproven whether these movements are of a truly migratory nature, involving annual population shift and counter-shift, or sporadic, irruptive, one-way adventures. However, I consider that the circumstantial evidence for the former is becoming ever stronger.

Furthermore, I believe that the influx of such large numbers in 2015, so soon after the 2013 event, does suggest that the species is undergoing a significant change in either its geographical range or its behaviour, with the former being more likely. I suspect that the butterfly’s southern belt of permanent residency in Europe is shifting northwards in response to climate change, and that its annual forays are therefore reaching further north into mainland Europe and, happily, into Sussex and the wider South of England, both more regularly and in greater numbers.

Only the passage of time will determine whether this theory holds water, but while so many of our resident butterflies are facing serious problems, some of which are likely to be exacerbated by climate change, it is exciting to speculate that species such as the Long-tailed Blue may be more likely to grace our shores in the future.

The formerly once-in-a-lifetime encounter with a Long-tailed Blue will never disappoint, as the butterfly seems to bring with it a taste of the Mediterranean and, for many, memories of holiday encounters. It has a characteristic, rapid, hairstreak-like flight pattern, making it difficult to follow, particularly when the highly pugnacious males launch themselves headlong into combat. Whereas other species are pursued at low-level, rival Long-tails zip rapidly skywards in vertical jousts, rather like the Duke of Burgundy.

The male’s wings are variable shades of lilac-blue, with a strong purple tinge in some lights. The appearance of particularly the forewings differs according to illumination, due to a dense covering of reflective blue hairs over the inner zones. Narrow brownish black borders run down the outer edges, inside the white fringes which rapidly begin to disintegrate on emergence.

The female is a duller, slaty blue with broad brownish black outer zones; they are variably dusky. Both sexes have tails, extending from the rear, inner corner of the hind-wings. These are black with flattened white tips which catch the slightest breeze, causing them to wave around and mimic the antennae of an insect. In conjunction with a pair of black eye-spots near their base, these provide a mechanism for distracting a bird strike away from the body parts.

The undersides of both sexes are similar, comprising a rather beautiful arrangement of swirling, fine bands in shades of pale brown and white. The black eye-spots near the tail are highlighted with silvery turquoise and edged with orange.

When the Long-tailed Blue does appear on Sussex soil it is usually seen in domestic gardens, allotments, on wasteland, along railway embankments, and over stretches of downland around the urban fringes. It has demonstrated a remarkably close association with Broad-leaved Everlasting-pea, on which the larvae feed, with some evidence that it has also used Broom at Seaford. However, the ease with which extensive stands of everlasting-pea can be located, and the tendency of most observers to follow previous sightings of the butterfly, dictates that there has probably been a significant recording bias involved. It is likely that some of the Long-tailed Blues which have hatched here in recent years have been raised on other leguminous plants.

The Pre-2013 Sussex History

In his comprehensive account of the butterflies and moths of Sussex, published in 2011, Colin Pratt collates a total of only 22 naturally occurring Long-tailed Blues, together with wild and imported (in leguminous produce) larvae, prior to 2013. He recounts the controversy which surrounded the first sighting of the ‘Brighton Argus’ in 1859, quoting from a 1862 manuscript: “… a very small clique of savants will not allow it to be put on the list as a new British Butterfly, because they have a theoretic fancy that it might be blown over from the coast of France, a distance of nearly a hundred miles, across the English Channel. The idea, however, is absurd”.

Since then, the highest total of adults achieved in Sussex was just five, during the great 1945 invasion of exotics. There is circumstantial evidence to suggest that the species bred here that year. The events of both 2013 and 2015 would individually surpass the entire historic record for the county.

The 2013 Event

Chris Glanfield set the ball rolling, when he noticed a faded and tail-less female nectaring on a pea plant growing in an Arundel garden on 8 August. The Arun Valley proved to be the most westerly limit of the 2013 Sussex landfall. The following day provided the most easterly sighting, when Trevor Buttle watched a female laying eggs in his garden at Pett. Ova were, however, subsequently discovered further east at Winchelsea (and to the west at Brede) by Ralph Hobbs.

The immigration continued through August, with further adult Long-tailed Blues being seen at Brighton (23 August), Newhaven (17 and 28 August), Seaford Head (31 August) and Northiam (20 August). A number of eggs and larvae were discovered, some of which were taken into captivity for study, or monitored in-situ. This led to a number of interesting observations on the species’ life cycle.

Following a two week hiatus, fresh, Sussex-bred Long-tailed Blues started to emerge, causing great excitement. These appeared, in date order; at Eastbourne (Birling Gap and later on the town’s seafront) between 16 September and 6 October; Newhaven (the town, including the Denton area, and Tide Mills) between 20 September and 12 October; Beeding Cement Works between 27 September and 6 October; Bury Village on 27 September; Alfriston on 29 September; Seaford (Buckle Bypass, East Blatchington, Hope Gap and Blackstone Bottom) between 30 September and 8 October; Southwick Canal (Shoreham Harbour) between 2 October and 12 October; Small Dole on 6 October; Brighton & Hove (Whitehawk Hill allotments and areas adjacent to the transmitter mast) between 7 October and 24 October; and Polegate on 22 October.

Butterfly watchers arrived in Sussex from far and wide, all hoping to see this exotic species, and many did. Amongst the local community of enthusiasts a small group of particularly dedicated Long-tailed Blue hunters soon formed, all of whom made important discoveries of either adults or early stages. This band included David Harris, James Arnott, Bob Eade, Nigel Kemp, Mark Colvin, David Sadler, Colin Knight and Steven Teale, many of whom went on to invest a large number of hours in the subsequent 2015 hunt, joined by others.

Using a very cautious and conservative approach in determining the tally of individual butterflies reported, so as to eliminate even the slightest chance of double-counting, Colin Pratt declared a Sussex total of 12 primary immigrants and 53 home-grown Long-tailed Blues, the former flying between 8 August and 31 August, and the latter between 16 September and 24 October. The real total may well have been higher, and a large number must have gone undetected.

The highpoint amongst these sightings was a cluster seen buzzing around an inauspicious patch of Bramble and Broad-leaved Everlasting-pea, growing beside a bus shelter on the Buckle Bypass on 2 October. James Arnott watched in amazement as a mating pair of these rare and exotic butterflies was repeatedly pestered by another amorous male.

However, no further sightings were made in Sussex beyond 24 October, and the Long-tailed Blue had no prospects of surviving our winter, due to the intolerance of its early stages to low temperatures, and lack of hibernation strategy. This tolerance was to be tested during the butterfly’s 2015 return.

The 2015 Event

As with the 2013 invasion, a well-documented build-up of Long-tailed Blue numbers was observed in both France and Belgium, in advance of the landfall along the South Coast. The butterfly was atypically numerous in Brittany and Normandy during the first weeks of August, and a large influx was again observed in Belgium, particularly from 7 August onwards.

Accurate dating of the butterfly’s arrival in northern mainland Europe, together with sparse records on the South Coast outside of Sussex, suggests a very similar timing to the main thrust northwards in 2013. However, in 2015 the influx into Sussex and the wider South of England appears to have stalled, due to the collapse of the weather in August.

The migration seemed to lose impetus, and although it later picked up with improving weather, this hiccup may have deprived us of an even greater influx than that observed in 2013. It also led to a significant delay in the development of the autumn brood on Sussex soil, and much of its tail-end most likely perished with the drop in temperature through October and early November. Adults of the immigrant wave were recorded between 28 August and 12 September, although eggs were discovered as early as 21 August.

Long-tailed Blues were observed in many of the same locations in which they appeared during 2013. This uncanny ability to repeatedly seek out highly localised patches of favourable habitat from year-to-year has been noted in Switzerland, by Guy Padfield. However, additional sites were recorded this year, with the landfall clearly demonstrating a greater westerly bias. The new venues included West Wittering, Bognor Regis (Hotham Park and a residential garden), Worthing, Lancing (railway embankment and communal gardens) and central Brighton & Hove (Royal Pavilion Gardens).

By now the investigative team had become highly adept at locating the eggs of the Long-tailed Blue, and I personally discovered them at eight locations between Bognor Regis and Seaford, on the majority of pea plants searched along a 50km front; this included 57 ova on just two plants in a Bognor garden, with nine on just a single raceme of flowers. Dr Dan Danahar and Mark Colvin found 82 over one hectare of rough grassland on Whitehawk Hill (Brighton & Hove). In all, nearly 200 were searched out.

Knowing where these eggs had been laid, and approximately when, allowed the highly focused pursuit of emerging adults, which began on 19 September at Newhaven Tide Mills. However, it soon became clear that adjustments had to be made to the duration of the life cycle, as it slowed from just six weeks to more than eight, in response to falling temperatures. In warmer climes this period can be as little as four weeks.

The Sussex-bred adults seen in the autumn of 2015 were restricted to sites along the coastal strip between Lancing Station and Newhaven Tide Mills, although it is unlikely that many enthusiasts were searching elsewhere, either in Sussex or further afield. The species was certainly under-recorded in Kent that year.

As temperatures dropped sharply at times during early and mid October, fears grew that the home-grown brood would perish before emergence, as the early stages are intolerant of cold. The weather station at Shoreham recorded night-time minima of 5 deg. C on 8 October and a worrying 4 deg. C on 13 October. However, a wide variety of factors are likely to influence the temperature actually experienced by larvae and pupae on different sites. Some survived, and Long-tailed Blues were still hatching on 1 November.

The low temperatures experienced at critical points in the butterfly’s life cycle may well have influenced the variable appearance of a bleached design over the hind-wings in some individuals, this being most strongly developed in the aberrant form typicafasciata seen at Lancing Station on 25 October.

The last of the season was observed on Armistice Day on Whitehawk Hill, where the experiences of 2013 and 2015 suggest that the life cycle is slightly slower than elsewhere, probably due to the elevated and cooler environment. By now at least 38 Long-tailed Blues had been recorded in Sussex, making 2015 the second best season for the species by some considerable margin.

When to Mate?

In ‘The Butterflies of Britain & Ireland’ (2010) Professor Jeremy Thomas states that “As a general rule, regular migrants such as the Clouded Yellow, Painted Lady and Red Admiral fly to the British Isles as virgins fresh from the chrysalis, and mate shortly after arrival. This cannot be the case with the Long-tailed Blue, for immigrants are so rare that the chances of a male and female encountering each other on arrival are negligible”.

Based on our observations in Sussex and further afield (particularly Kent) in 2013, this certainly seems to be the strategy adopted under more favourable circumstances, as there is evidence to suggest that freshly emerged, British-born females were immediately mated, before apparently emigrating southwards, carrying a cargo of fertilised eggs with them (see ‘Evidence of Reverse Migration?’).

On 8 September 2015 James Arnott contacted me to say that he’d found a small, mixed-sex group of immigrant Long-tailed Blues on the outskirts of Seaford. While en route he provided an update; two of the butterflies were now mating. I arrived just in time to witness the last few minutes of this historic event. Any sighting of a mating pair of Long-tailed Blues in the UK is rare enough, but this was occurring within the immigrant wave. Although believed at the time to be the first example of such behaviour, it transpired that the same had been observed at Kingsdown Leas (Kent) on 3 September.

Both of the individuals involved in the coupling at Seaford were clearly of considerable age, and showed significant wear and tear sustained over their long journey. In some species, such as the Green-veined White, the repeat mating of females is well documented, and not always designed to fertilise eggs, as the essential component in some of these exchanges is life-extending nutrients.

For the female Long-tailed Blue at Seaford this did indeed prove to be a second act of copulation, for within ten minutes we watched her lay an egg (indicating that she had been mated in advance of this coupling). It is therefore apparent that this species will sometimes mate on arrival at its migratory destination, although it remains unclear whether this is for strictly reproductive purposes. Either way, the act is likely to maintain the reproductive health of the females, while enduring very long and arduous journeys.

Evidence of Reverse Migration?

Close observation of the Long-tailed Blue in 2013 and 2015, both in Sussex and further afield, has provided a growing body of circumstantial evidence suggestive of a return migration southwards in the autumn. This can be summarised as follows.

Atypically for most butterflies, female Long-tailed Blues emerge before the males, at least during the autumn generation, while at the northern limit of the species’ geographical range. The observed sex ratios changed markedly during the home-grown flights, becoming heavily dominated by males during the later stages.

It would be potentially advantageous for females to emerge ahead of males during the autumn, assuming their intention was to emigrate southwards as soon as possible, following fertilisation of their eggs. A head-start on the males would allow them the opportunity to take on reserves and become fully flight-ready, in advance of copulation.

2013 Female:Male Ratio
16 September – 1 October 2:1
2 October – 24 October 1:3

2015 Female:Male Ratio
19 September – 25 October 2.5:1
26 October – 11 November 1:3

In 2013 the autumn brood females were invariably photographed in perfect or near-perfect condition and seldom, if ever, repeatedly; they seemed to rapidly disappear. However, many of the males were photographed over the course of a number of days, exhibiting increasing wear and tear. They appeared to remain faithful to the areas in which they hatched, presumably in the hope of intercepting emerging females, although some sites rapidly emptied of male butterflies later in the autumn flight period.

In 2013 the butterflies behaved in a colonial manner and mating was observed. However, despite a total of four autumnal pairings being witnessed, not a single egg was discovered, despite extensive searches in Sussex. Eggs had been remarkably easy to locate during the immigrant flight.

On 8 October I watched the last of the butterflies recorded from the Buckle Bypass colony disappear, flying high and fast from the top of the embankment and southwards over the A259. At this time Long-tailed Blues were appearing at sites on the coastline, including the Languard (6, 7, 8 October) and Dungeness Bird Observatories (8 October), and later at Wheelers Bay on the Isle of Wight (15 and 17 October). It is tempting to suggest that such sites might represent exit points.

The pattern observed during 2015 was rather different. The autumn brood developed much later and under less tolerable environmental conditions, with temperatures dropping sharply and day-length rapidly shortening. The butterflies displayed no colonial behaviour, no courtship or mating was observed, and both females and males disappeared immediately, whenever the weather was conducive to flight. Apparent departures were noted around midday on several occasions.

Distribution

The western limit of the 2013 landfall in Sussex was marked by sightings made along the course of the River Arun, but the vast majority of butterflies were seen either in or east of the Adur Valley, with the highest density of records coming from between Newhaven and Eastbourne. A relatively small number came from further east, particularly around the Winchelsea area.

The 2015 landfall demonstrated a more westerly bias, with records coming from the coastal strip between West Wittering and Seaford. The Long-tailed Blue was only rarely seen further than 10km from the sea.

Abundance

The Long-tailed Blue was usually observed singly as a primary immigrant, but occasionally in small mixed-sex groups. When the main influx occurred sufficiently early to allow the development of viable autumn colonies, these gave rise to clusters of more than half-a-dozen individuals.

Flight Period

In 2013 the immigrant wave flew between 8 August and 31 August, followed by a home-grown brood observed between 16 September and 24 October. In 2015 the first immigrants must have arrived in Sussex sometime prior to 21 August, when the first ova were discovered, and these voyagers flew until 12 September. There followed a protracted emergence of Sussex-born butterflies, detected between 19 September and 11 November.

Taking the two years together, the immigrant waves occurred between early August and early/mid September, followed by home-grown broods persisting between mid September and mid November, with the timing of events being dependent upon the date of first arrival and subsequent weather patterns. However, it is known that small advance parties may arrive in July, based on both the historical Sussex record and observations elsewhere.

Life Cycle

The following account has been drawn from the observation of Long-tailed Blues in 2013 and 2015, including the study of the early stages by David Harris in his Newhaven garden, and through captive-breeding by Mark Colvin.

The eggs are laid on Broad-leaved Everlasting-pea, Broom, and possibly a range of other legumes, with an apparently strong preference for the former in Sussex and wider South of England. The tiny white discs are deposited one at a time, although a female may lay a large number on a single plant. They are usually positioned on the calyx of a pea flower, but occasionally on young buds or a supporting stem. In warm weather they hatch after only a week and the caterpillar eats its way out through a ragged hole, leaving much of the structure intact. The remains of the egg are rapidly washed off the plant by heavy rain. At this stage the greatest threat to the early stages appears to be incidental grazing by slugs and snails.

The caterpillars initially feed on the internal, reproductive elements of the flower, entering through either boreholes made in the petals, or by slipping through the folds between them. When holes made in the petals are open to the exterior, the caterpillar will spin a protective silk window across the void. The same technique is used to secure any openings in the pods of the plant, into which more mature caterpillars move, feasting on the peas and softer lining.

The slug-like larva is off-white with broken, pinkish brown chevron markings. It undergoes a total of three skin-moults and the more mature caterpillars may be enthusiastically attended by the black ant Lasius niger, which is probably attracted to the honey-gland on its tenth segment.

When full-grown the larva turns a deeper lilac-pink colour and seeks out a pupation site either on withered leaves or pods of the foodplant, or on vegetation some distance away. The elongate, cream-coloured chrysalis is lightly speckled and secured with a silk girdle. It turns a dark inky blue prior to hatching. The duration of the entire life cycle is highly variable, being strongly influenced by temperature.

[selbypaul]

Thanks for reproducing that entire species account from the book Neil. It really is impressive. And fascinating too! I've been following your posts on this topic since 2013 and I still learned a lot in this most recent post.

[Neil Hulme]

Thanks, Paul. I'm glad the species account was helpful. I'll have to write an update at some point, to include the huge amount of post-2015 data and observations.

Roger, going back to some of your questions which aren't covered in that account. The Long-tailed Blue, like other unrelated migrant species, has adapted to behave in this manner (despite the considerable effort involved in long distance travel) as it benefits greatly by being able to track environmentally favourable breeding conditions. 'Sedentary' species must contend with more local weather patterns, including drought, which makes them more susceptible to boom & bust. There's a trade-off involved in adopting either modus operandi but, on balance, obligate migrants are set to do rather well, particularly in this rapidly changing world.

The Long-tailed Blue's ability to utilise a very wide range of larval foodplants (which now includes Wisteria in the UK) confers obvious advantages. This species demonstrates a high level of behavioural (and particularly reproductive) plasticity, which is a common feature in highly successful species.

It is also a superbly adapted flying machine; I see it as the Hawker Sea Fury of the butterfly world, so it's perhaps unsurprising that it's one of the most successful and geographically widespread species of butterfly on the planet.

BWs, Neil

[Pete Eeles]

I really enjoyed reading your writeup, Neil - great stuff! As usual, some very insightful observations to complement your superb photos.

Cheers,

- Pete

[Neil Hulme]

Thanks, Pete. I think there's plenty more to come this autumn, in a year which will prove to be a stand-out for exotic migrants. Although Kent hasn't received significant numbers of Long-tailed Blue this time around (I suspect the Spain – Pyrenees – western/central France – Brittany/Channel Isles/Normandy route has out-performed the Italian Peninsula – Switzerland – eastern France – Nord Pas de Calais/Low Countries route), it's done rather well with Queen of Spain (now emerging in numbers as a British brood) and gorganus Swallowtail (which will surely emerge on Kentish soil next spring). Add to that the recent influx of Camberwell Beauty from the east, and we have a highly impressive line-up. I've also heard a relatively recent report of a Large Tortoiseshell on the beach at Newhaven.
BWs, Neil

[Neil Hulme]

6 & 7 September 2022

On 6 September I received a phone call from the owners of the Bognor garden which has hosted Long-tailed Blues continually since 8 August, comprising several waves of primary immigrants and the emergence of home-grown adults. A freshly emerged female was being mated by one of the primary immigrants (three males) which arrived in the garden on 4 September. I knew that I had just under an hour to get there, as the species typically remains paired for this period. The traffic was kind to me, so I enjoyed about five minutes with the happy couple before they went their separate ways. A male also emerged in the garden that day, although I wouldn't see him myself until the following day.

Following another phone call, I spent the morning of 7 September in the garden. The garden-born female (emerged and mated yesterday) and garden-born male (emerged yesterday) were last seen at 11.15am, presumably flying south. This left just the three primary immigrant males on-station. I had to leave around midday, knowing that the afternoon would likely host more action ... it did.

The owners kindly provided their regular evening update, including the images required to confidently recognise individual butterflies. During the early afternoon, 'new' garden-born female and male Long-tailed Blues emerged, with the former being mated by a primary immigrant, while the latter did his best to break into the party with a flurry of wings and flailing abdomen; he of course failed.

On this day alone, the garden had hosted seven individual Long-tailed Blues, including two garden-born females, two garden-born males, and three primary immigrant males.

[David M]

...Queen of Spain (now emerging in numbers as a British brood) and gorganus Swallowtail (which will surely emerge on Kentish soil next spring). Add to that the recent influx of Camberwell Beauty from the east, and we have a highly impressive line-up. I've also heard a relatively recent report of a Large Tortoiseshell on the beach at Newhaven.

Yes, it's quite some year for exotica on home soil, Neil. I wonder if we'll get a Southern Small White or maybe even something totally unexpected, e.g. Bath White?

[Benjamin]

Superb updates as always Neil.

I just wanted to push you a bit more about your theory of ‘reverse protandry’. I was going to leave it for something to deal with in the pub, but thought others might be interested in some more info/discussion so decided to quiz you here…..

From the observations that have thus far been made I can’t quite get my head around males emerging later than females in this context. Surely the same advantages as usual would apply to early emerging males if females are willing to copulate (as we know they generally are) before heading off south?

I think you’ve suggested that perhaps females could gain an advantage by speeding up development and allowing themselves time to fuel up pre departure ahead of any matings? I have a few queries about this. Firstly i would have thought both sexes were developing at max possible speed under the mid/late season conditions so I’m not sure how females could get ahead in this regard? I don’t have much of an understanding of biological processes but would assume that protandry in the usual sense is achieved by a slowing down of development in the females? That may well be an oversimplification or just plain wrong but the main question of how females could out develop the males still remains. If we assume that there is scope for accelerated development then why wouldn’t males follow the same path? As mentioned earlier if fresh females are emerging and are accepting mates then surely male genes will do best by timing male emergence slightly ahead of the females as usual? In the quest for freshly emerged virgin females, any kind of retarded development in males seems an absolute non starter - especially if the target females plan to sod off at the first available opportunity!

Secondly if females are to mate and take on fuel pre departure then why does it matter in what order they complete these tasks? Why is it an advantage to be out ahead of the males? Of course if they don’t plan to mate until touching down somewhere south then I suppose avoiding the bothersome advances of amorous males might help to some extent, but this doesn’t seem to tally with the bulk of the observations we’ve made, and presumably it wouldn’t be hard to find fuel away from the concentrations of males anyway.

I appreciate your suggestion is driven by the excellent data you’re collecting, but is it possible that the differing behaviour of males and females is skewing the data?

For example the observations of more males later in the home grown flight are surely the result of the male tendency to hang around at a site waiting for females to emerge whereas females quickly mate and depart.

Of course the tricky bit is explaining why you seem to be finding fresh females emerging ahead of males early on in the flight period. Perhaps early emerging males travel more widely in search of females and so go unnoticed? Or perhaps they move to lekking sites straight away whereas females fuel up on nectar close to where they emerge first? I guess there could be a number of possibilities here.

Anyway - this is very easy to settle. We just need to collect some LTB eggs next year (if they arrive……) and raise them under natural conditions. Perhaps this has already been done in order to study the lifecycle? Do we have results for this?

BTW I would sincerely like your theory to be right as this would be, to my mind, by far the most intriguing scenario.

A couple of possibilities that could lead to males emerging later (delayed male development) come to mind.

The most straightforward is that if females mate multiple times and remain at the breeding grounds for some time then clearly the premium on virgin females is reduced, and males could maximise fitness by emerging at the point of highest female density thus enabling the maximum number of matings. The observation that females quickly depart seems to completely undermine this possibility, but we must remember that we’re only focusing on what what we observe in the UK, at the extreme limit of the migration and under very unusual conditions. Could it just be that LTB always exhibits protogyny and it is the promiscuous nature of the females that gives rise to it?

Anyway - I think I’ve clogged up your otherwise clear and concise diary with my ramblings enough for one day!

[Neil Hulme]

Hi Ben. This is a fascinating and complex topic, but one which must wait until winter for further discussion. My ecological and guiding work is of such a seasonal nature that I have very little free time at this time of year and those precious hours when I manage to wriggle free from work and family commitments are best invested in recording LTB while it’s still flying; there’s plenty more action to come, and more data to collect, so theory and discussion must wait until quieter times. I know I posted a long one in response to Roger’s points, but that was an easy cut & paste job.

You’ve asked so many questions that it will take an essay (probably several) to respond properly, and my answers will probably generate more questions. It takes a superhuman effort to try (and often fail) to keep my diary flowing at this time of year and if I were to embark on this now, that side of things would inevitably grind to a halt. So, please bear with me and I’ll respond once Knepp has closed for the year and any early deadlines for summer work reporting have passed.

BWs, Neil

[Neil Hulme]

11 September 2022

A brief visit to the Bognor garden on 11 September didn't provide much action with adult Long-tailed Blues (just one ageing garden-born male present) but the owners excitedly announced the discovery of a larva, located in a rather exposed position within an open flower. The mature caterpillar appeared to be 'silking-up' prior to pupation. However, despite clearly being full-grown, it was neither the expected lilac colour, nor in a location that I would consider suitable for completion of the life-cycle, not least because the flower would likely wither, die and fall before eclosure (see Colvin, M. (2014). Rearing the Long-tailed Blue - Personal Observations [Online]. Available from http://www.dispar.org/reference.php?id=5). Something wasn't quite right.

The following day, the owners sent me an image of the hapless larva. All was not well, and although the image was not clear enough to determine the nature of the culprit, this was undoubtedly the work of a parasitoid. I asked them to place the corpse in a sealed container and an investigation will be conducted in due course.

[Benjamin]

That’s fine Neil! Something resembling that post has been floating around in my notes for some time - I just finally found some time to mould it into something reasonably coherent. So yes - I agree any resulting back and forth would likely be disjointed and ruin the flow of your PD. The trouble with the pub though, is that if we don’t get it cleared up by pint 4 I’ll have forgotten what it was that I didn’t understand in the first place.

[bugboy]

CSI: Bognor Regis. The first episode will certainly be of very niche interest for sure!

[Roger Gibbons]

King George V clearly didn’t appreciate Long-tailed Blues else his (alleged) last words would have been different.
Roger

[Neil Hulme]

Thanks, Ben. I think I'll be able to answer most of your questions when a little more time appears, but I don't think that will include what drives protandry or protogyny at the cellular level (without research). I'm looking forward to those winter pub sessions!

Hi Paul. It probably won't be as popular as 'Real Housewives of Bognor'.

Much myth surrounds the last words of King George V, Roger. His last words were actually "Bugger Butlins".

BWs, Neil

[Neil Hulme]

12 & 15 September 2022

With my brother visiting from Antwerp, I escaped from work for an entire day to go butterfly-hunting with him on 12 September. Whitehawk Hill seemed an obvious choice and the place was pretty quiet for a change, with the exception of Our Trevor and a visitor from Dorset. She had already spotted her first-ever Long-tailed Blue with Trevor's help.

After many hours searching, we came away confident that there were just two primary immigrant males flying that day; one either side of the transmitter mast. However, the highlight was provided by a freshly emerged female. She did very little throughout the day, spending long periods in shut-down mode, with her antennae held parallel and tight together; occasionally she would stir and make a short flight to find nectar. I suspect that she would have started her long journey south, mated or not, before 1pm the following day. (I did come back to alert you, Trevor, but unfortunately you had left the site just a couple of minutes earlier )

Between leading safaris at Knepp on 15 September, I managed a quick dash to Whitehawk Hill, to see if any 'new' LTBs had emerged. The weather never played ball, but I did find the sad remains of a female in a spider's web.

[Neil Hulme]

17 September 2022

Firstly, I must thank Claire and Nick Oliver for finding and reporting their two Long-tailed Blue males on Worthing seafront on 16 September; this has triggered a remarkable string of further sightings which add to our understanding of this species' adventures on British soil.

With just a couple of hours free between morning and dusk safaris at Knepp on 17 September, I headed to Worthing seafront with, I must admit, quite limited expectations. It transpired that other observers had seen up to three LTB flying around the Tamarisk windbreaks on Worthing promenade, opposite Seaview Road, earlier that day. However, between 2pm and 4pm I photographed five different males along an 80 metre stretch of the 'hedge'. Even better, a female suddenly appeared and despite an initial reluctance to succumb to the advances of a male, was eventually mated. On two occasions another male discovered the pair and attempted to break-in on the party.

I later bumped into Lindsay Morris, who had been out on a similar mission. He reported having seen a male much further east earlier in the day, and had just come from further west along the seafront (the base of George V Avenue), where Dave Broxham had found another. The presence of at least seven males and a female spread quite widely along the beach, all within 100 metres of the water, hinted quite strongly at what might be happening here, particularly in the absence of any immediately local larval foodplants. The following day would contribute much more to this developing picture.

[Neil Hulme]

18 September 2022

18 September really was a day to remember, spent in the good company of friends including Sue & Dave Broxham, Leigh Prevost, Gary Faulkner, Paul Atkin and my brother Mark. Worthing seafront felt like the Mediterranean, both in terms of the weather and the numerous exotic butterflies we saw along a 1.75 km stretch of the back-beach.

Paul and I made the most exhaustive search, heading westward to Goring-by-Sea. We had started the day on the prom near Seaview Road, where three quite tired looking Long-tailed Blue males were still whizzing up and down the Tamarisk windbreak. We then found a single male nectaring on the beach just west of Grand Avenue.

But the best action was to be found west of George V Avenue, where at least a dozen Clouded Yellows, including helice, and a few Humming-bird Hawk-moths joined the LTBs on Costa del Worthing. Between here and Goring-by-Sea I saw a minimum of 14 LTBs, including two females (a beauty in front of the Sailing Club), bringing my day tally to at least 18 individuals.

By now it was becoming ever clearer that LTBs were congregating along the beach before making the journey south across The Channel. I saw one head fast and low towards the shoreline but couldn’t be certain that it had actually ventured out to sea. However, their departure across the water would be confirmed several times over the next couple of days.

I suspect that we have become a little too focused on feral Broad-leaved Everlasting-pea in our searches for LTB, as the distribution of these butterflies suggests that they have probably arrived here from the gardens and allotments of Worthing and its outlying settlements, raised on a wide variety of leguminous foodplants including Wisteria, although I’m sure that BLEP will have played its part. Unsurprisingly, LTBs are also being seen on the beaches around Bognor, with Tony Hill reporting sightings at Aldwick.

The invasion of butterfly-watchers has attracted great interest from passers-by and some of the local residents. Claire, whose garden opens onto the hotspot, has been out every day with her camera and has plans to plant some Bladder Senna and Lucerne. It appears that I may have underestimated the charms of Sunny Worthing.

[bugboy]

A bonkers day, you wouldn't have thought things could get even better......

[Old Wolf]

Neil, your diary has been very enlightening and I am very much enjoying learning about the LTB's down south. The last entry sounds like an amazing day was had by all. I am incredibly envious.

I am hoping it continues as I am considering making the trip myself on Sunday as it looks like the best day weather wise. Until then, I am keeping everything crossed and will be watching your diary like a hawk