The Butterflies of Hadlow - an introduction.

Hadlow near Tonbridge in West Kent is a great parish to spot butterflies in, with a good selection of resident species and always the possibility of some exciting vagrants and migrants moving through! There are some very good patches of grassland and woodland habitat scattered throughout the parish, from the River Medway in the south, to the Ancient Woodland of Dene Park in the north. These habitats are under continual pressure, from development and perhaps more intensive farming, and are well worth maintaining, or where possible extending.

It is in Dene Park where the star of Hadlow's butterflies, The Purple Emperor can be seen, sometimes in close-up with stunning views, in its brief flight period in the summer, but it is the diversity of habitats throughout the parish that make it an endlessly fascinating place to study butterflies, and much other wildlife, almost all year round.

I am working on a gallery of the Butterflies to be found in Hadlow - when it is done you will be able to scan down the pictures and click on the picture of a Butterfly you think you have seen for more information!

And here is a list of the Butterflies you are most likely to see in the Parish of Hadlow, again with the onward links for further information!

The Whites: The Brimstone, Orange Tip, Green-veined White, Small White, Large White and the Clouded Yellow.

The Browns: The Meadow Brown, Gatekeeper, Speckled Wood and Ringlet.

The Blues: The Common Blue, Holly Blue, Brown Argus and Small Copper.

The Vanessids: The Red Admiral, Peacock, Painted Lady, Comma and Small Tortoiseshell.

The large Nymphalids: The White Admiral and Purple Emperor.

The Fritillaries: The Silver Washed Fritillary

The Hairstreaks: The Purple Hairstreak and Green Hairstreak

The Skippers: The Large Skipper, Small Skipper and Essex Skipper.

What butterfly have you seen?

The Whites:

and the Clouded Yellow (powerful flyer, looks yellow-orange, could be anywhere in the Parish, most likely late summer to autumn)

       

The Nymphalids:

the Small Tortoiseshell (fair flyer, looks dark orange but much darker underneath, most places in the Parish such as gardens and farmland, mainly mid-summer to autumn but throughout the year)

   

The Gatekeeper, Pyronia tithonus

Gatekeepers galore! After the tension of "the June gap", the Gatekeeper appears in numbers in early- to mid-July to help signal the "Butterfly Bonanza" of late summer in woodlands, hedges and larger gardens all around the parish. It is a medium-small sized orange-brown butterfly generally seen fluttering over hedges or nectaring on brambles. It is most easily confused with the Meadow Brown, but it is brighter orange by contrast, slightly smaller and more commonly seen in hedgerows, more rarely in open grassy areas.

There is just one generation and their flight period is virtually over in 6 - 9 weeks, by the beginning of September. On average the males emerge before the females. Each individual has a lifespan of only about 3.5 to 8 days.


Description

When viewed from the upper-side, the orange patches on the brownish wings are fairly obvious. The next point to look out for, if you can get close enough, are the two white spots in the dark eye, where the similar Meadow Brown usually (not invariably) only has one white spot.

This is a fairly typical upper fore wing, and this is probably a male, with a sex-brand in this species of a dark smudge in the centre of each fore wing, which the females do not have. On this specific insect there is a greenish wear mark as well, indicating this butterfly has probably been around for a few days already. Males are smaller and darker on average than the females. Both sexes have the clear brown bands around the outer edges of both of the wings, with a neat tiny fringe of hairs at the wing edge, nice and even when fairly fresh.

When viewed from the underside the fore wing is largely orange, with the (generally) two white spots in a dark eye, while the hind wing is a subtler pattern of browns and greys with a characteristic sharply "eared" pattern to the boundary between the darker front and the lighter back, a whitish patch about midway along the top edge of the wing (this sometimes looks like Bart), and several (2 - 5 normally) small white flecks in a semi-circle in the two darker areas somewhat to the rear of the hind wing, all of which helps to distinguish this butterfly from the somewhat larger, browner, duller, but otherwise quite similar Meadow Brown, which has black flecks. In my limited experience the lowest white fleck, if present, tends to show through onto the upper side of the wing as well as the lower, but the upper ones do not, however clearly they appear on the lower side.





Here are several Gatekeeper "faces" - this butterfly often has a "surprised" look on its face:

Distribution

Good places to find Gatekeepers in Hadlow are many of the woodland or shaw edges, often where footpaths enter the woods (- so-called gateways - how the butterfly got its current name of Gatekeeper) and also most of the larger hedgerows rich in bramble or other flowers - the open flowers of brambles if available are particularly popular with Gatekeepers which (for butterflies) have a rather short proboscis! As the Gatekeeper season progresses through August bramble flowers become harder and harder to find, and the butterfly moves on to other flowers. The Gatekeepers share their flowers with other species of butterfly such as Meadow Browns, but only the Gatekeeper carries such relatively bright orange markings overall on an otherwise brown medium-to-small-sized butterfly! The Gatekeeper is absent from the northern half of Britain and most of Ireland, but is very common in the southern half of England, perhaps being the commonest butterfly in Devon and Dorset.

The male Gatekeepers have been found to search, inspect, engage potential mates, and perch (bask and rest) on shrubs or shrub edges significantly more frequently compared with male Meadow Browns, but do move off the shrub edges if they need nectar for example. Similarly, female Gatekeepers perch on shrubs and oviposit at shrub edges more frequently than do female Meadow Browns. This fits in with ecological theory, which predicts that the butterflies with the brighter "eyes" (the Gatekeepers) will tend to be more greatly associated with scrub and woodland.

The ideal combination is a large hedgerow, woodland edge or track with tall wild grasses (the larval food plants) flowering along the base of the shrubs. One such bountiful hedgerow is to the East of the farm reservoir beyond Malt Cottage, reached by footpath from Victoria Road or by footpath via Style Place from Court Lane, but hedgerows of reasonable size along one of the many public footpaths may often have anywhere between one and a hundred Gatekeepers sunning themselves, only to be startled into flight by our approach. Other good footpaths are those between the College's Equine unit and along the River Bourne, the footpath along the north bank of the River Medway between Hartlake and Tonbridge, the southern half of the Access Trail, the footpaths through the Oxenhoath Estate, and those around Pittswood. The best hedges are of reasonable size, not tightly trimmed every year, have large and diverse headlands with alternate nectar sources, and are not directly neighbouring arable crops subject to spraying, or intensive grassland.

However not all apparently suitable habitat does actually hold Gatekeepers. Research In Belgium confirms this, particularly in comparison with the virtually ubiquitous Meadow Brown. I think that the same is true on a micro-scale in Hadlow. Some hedge sections contain several individuals (small colonies) but others apparently just don't, despite appearing quite suitable. It is possible that this is due to a relatively slower establishment rate in this species, so that local accidental extinctions are "re-filled" at a slower rate in the complex agricultural matrix, leaving some habitat opportunities temporarily unfulfilled. Alternatively, it may just be that habitat is not always suitable at any one time, and we simply do not understand why not, or indeed the factors that are required for good habitat. Shelter may be more important for many butterfly species than we have realised to date, and we still know little of the requirements for nectar sources, larval food-plant requirements, temperature and rainfall factors, to mention just a few.

In and around woodlands Gatekeepers are also often found feeding on the brambles, knapweeds, thistles, fleabanes, ragworts and other fairly open flowers close to the shrub edges where they have their territories. a good example is along the sunnier tracks of Dene Park which is completely Public Access. (From the Puttenden Road car park take the main track and either turn left along the track into Knight's Wood (best), or check out the first section of the track straight ahead of you). They are also common along the sunnier footpaths through and around the edges of Clearhedges Wood in West Peckham Parish, which you can reach by crossing the road CAREFULLY. When flowers are scarce Gatekeepers may feed on the honeydew available higher up in the canopy in woodlands;

The Gatekeeper is thought to be quite a "static" and "home-loving" butterfly despite being a good strong flyer, and apparently spending more time on the wing than other species such as the Meadow Brown. The colonies are fairly self-sufficient, and do not appear to intermingle much in comparison to other species. When artificially moved or displaced the individual butterflies have a preference for returning to their familiar haunts, even tending to cross railway lines to return to their "own" side! However on occasion short and long distance movement does occur, so colonisation of new sites clearly can occur on occasion.

Each hot-spot therefore depends on its own habitat quality being maintained, although Gatekeepers will often briefly also use resources outside their home-range and these may indeed be vital to them! The butterflies found in gardens generally come from hedgerow colonies nearby. However there are large patches of the parish where there is no habitat close by, and the butterfly is almost never seen - for example it is only rarely seen in my garden although my house backs onto the hedgerows along School Lane and there is a small colony located in a sunnier section about 200 m away. It is also extremely rare in London, even in the parks, again perhaps because it finds it difficult to spread where suitable habitat is rare and well-separated by inhospitable areas.


Life cycle

The Gatekeeper has good years and bad years. Good years tend to be when the previous August was generally hot and dry, and 2014 was an exceptionally good year after the great summer of 2013! In addition, following a mild and wet winter (just like the recent 2013/2014 winter - an example of a "positive North Atlantic Oscillation") emergence tends to be earlier because of the warmer weather.

Over July and August the Gatekeepers mate and the females lay their eggs at the base of shrubs close to, or occasionally on, the sheltered grasses on which the caterpillars will eventually feed. The caterpillars first of all eat their own (protein) eggshell, then start eating the tender sheltered grass tips. Once the weather gets colder, the caterpillars hibernate (after the first of four moults) in the bases of the grass plants, resume feeding in March or April of the following year, and eventually form a chrysalis in June-July.


The white specks on the underside vary

It would be very interesting to find out if the white speck pattern variability is linked in any way to the individual colonies. E.B. Ford did some ground breaking work on the dark specks on the underside of Meadow Browns, on islands of different size versus the mainland which founded some fundamental ecological theory as a result.

This is an individual from the hedgerow to the east of the reservoir with nearly three white specks, one at the top and one half way down the wing, with perhaps a third below it.

This is an individual from the hedgerow colony to the north of Hope Cottage. It only has two white underside specks, this time both very high on the wing:

This is a  much more worn individual, with the start of a third speck lower on the underwing.

This is another individual, this time more clearly with three white flecks.

This is an individual from a hedgerow on the other side of the Bourne, between the college's equine unit and The Mill, with four white specks:

This individual from the nearby Tudeley Woods car park has four white specks, but unusually with three on the higher side and only one on the lower. As in most individuals, each speck seems to generate a brownish surround sometimes with a very dark immediate rim. Interesting developmental genetics!

Tudeley Woods, 17-07-2014

Oddities

The scales of a butterfly or moth are extremely varied in form and function. Some are specialised to be upright and fringed, the better to release the scent pheromones, such as those found in the male "sex-brands" mentioned in this and previous blogs, or in tufts in some other species, but some other scales are developed into extremely long hairs, as seen on the body and in these patches on the wings in this Gatekeeper. This perhaps explains why where on the insect you see the hairs you get fewer coloured scales (whether genuine pigment colours or refractive colours). The function of hairs is presumably primarily insulation - but I wonder how the presence of the hairs affects other things such as flight, and drag for example.



The hairs on the under-wing appear more vertically orientated away from the wing - is this gravity or not? It doesn't look like it. If it's a deliberate difference, then could it be for aerodynamic purposes?




Parasites

Like other species of butterflies, the Gatekeeper may be infested by bright red mite larvae of the species Trombidium breei or perhaps as originally identified Trombidium poriceps. About two thirds of individual butterflies are likely to be temporarily infested with mites at some stage in their short lives, perhaps for a day or so, males slightly more than females.  The mites come off the butterflies onto new flowers about as easily as they hitch rides, and although they do suck their host butterfly's blood, they don't seem to have a significant effect on their host's behaviour or survival.

The Meadow Brown, Maniola jurtina.

This is almost certainly the commonest butterfly in the UK, found wherever there is grass that is not regularly cut or heavily grazed. Generally brownish, the females are however much more brightly coloured and distinctly patterned than the males.


Description 

This is a lovely view of the underside of the wings of a Meadow Brown, probably a male from the relatively even colour of the hind wing, taken in Dene Park in 2011. This individual has got three dots on its hind wing.

This photo is of a fairly typical female, much more brightly coloured than the male, with a brighter forewing eyespot, but fewer dots on the hindwing:

This is another quite bright female, but this time with two black spots clearly visible on the hind wing!

This individual has a double eyespot, and so could be confused on first glance with a Gatekeeper. However, its other features confirm that it is a Meadow Brown, possibly a female, but with two "hind wing specks":

Distribution

Meadow Browns can be found almost all over the countryside in Hadlow, but are commonest wherever there is long grass in reasonable amount. They will be present wherever you look in pasture fields and meadows allowed to grow long, so that at least some of the grass is in flower. In suitable meadows you will find them regularly year after year, at densities of over 1 every 10 square metres. You will find at least some along almost every grassy road verge and field margin, and along most woodland paths and rides.

In Britain and Ireland they are found everywhere except the Highlands of Scotland, never in the Northern Isles, and rarely at high altitudes on the mainland. In Europe it extends throughout Europe and Asia as far east as Iran.

Meadow Browns are quite sedentary, but some will move, particularly perhaps the males, to find new habitat.


Life cycle

The first adults generally appear around the beginning of June, and numbers usually peak in around the second half of July. In some of the best sites however adults may still be found as late as September.

The males are the most active, and search assiduously for the newly emerged females. When found, the males cover the females in an odd, musky scent causing the female to settle quietly, ready to mate, which they generally do only once. Here the male is to the left, the female to the right.

Individual life span is generally around half a dozen to a dozen days, and the females are able to ripen their eggs and start laying in as little as 3 or 4 days, flapping jerkily above and among suitable grassy food-plants, fine or medium grasses. The eggs are laid on grass, or rather more carelessly, nearby. The grass chosen may be infected with fungi that the caterpillars can ingest and perhaps use themselves as bactericides. The small caterpillars feed by day, hibernating, until the spring, when, as they grow and become more obvious, they switch to feeding at night, sometimes at densities up to 10 per square metre. At this stage they are green and relatively hairy, with a tiny white projection on their tails. By June most caterpillars have pupated.


Oddities

The numbers and patterns of dots varies with gender and location, and the variation has led to considerable speculation on the evolutionary value of the traits associated with the spotting. The butterflies use their colours and patterns for both concealment and eliciting surprise, in ways that do not appear to have been fully elucidated to date, although huge amounts of data have been collected and about which a great deal of papers have been written. This very common butterfly still has a lot to teach us!

This particular female has rather exceptionally well-pronounced rear wing specks!

Haysden Country Park, Tonbridge, 05-07-2013

Predators and parasites

Birds are known to try and catch them - and often manage to get a nip in!

The Speckled Wood, Pararge aegeria

The Speckled Wood is a brownish butterfly of woodland paths and glades, perching low on leaves either side of paths and edges, fluttering up when disturbed. Depending on season and wear it can either be surprisingly colourful, or on the other hand, surprisingly dull!


Description

Although on first sight the Speckled Wood is a light brown spotted and streaked butterfly of woodlands, and in the south, of large dense hedgerows, on closer examination the pattern of colours is both subtle and beautiful, giving the impression of varying textures in different areas of the wings:

Holborough Marshes, 12-05-2014

Distribution

Any small piece of woodland, or a path with shaws of trees on either side, can hold Speckled Woods. The males are easy to see, holding their territories, and hopefully at least some females will pass by them all, wherever they are!

Trosley CP, 17-07-2013

The sex-ratio is likely to be roughly equal, but the males are much more easily noticed as they perch or patrol, while the females spend the most of their time skulking and hiding in the foliage of trees and bushes.

There is a fairly consistent daily activity pattern, and individuals tend to go to roost overnight as the sun falls, wings closed, on the underside of leaves, perhaps fairly high in the canopy. As the sun rises, it becomes necessary to bask, wings open on the upper surface of the leaves, until a body temperature of 32-35 C is reached, when the wings tend to be closed again to reduce the heat-gain.

In the summer there is plenty of honeydew on the leaves and many of the butterflies feed off this energy source. Later in the season there is less honeydew and the Speckled Wood individuals around then are more likely to be found nectaring off quite a wide range of flowers.

Individual males may be either "perchers" or "patrollers" and differ in physical shape and colouring according to their preferred mating strategies.


Life cycle

This lovely butterfly has two or possibly three generations in a particular year, a spring generation March to May, a summer generation over quite a long period, June to September, peaking about late August and a probable small third generation in October. Whether caterpillars about to pupate in the summer do form that third generation or not appears to depend largely on day-length, secondarily on temperature, but also on the genetics of that particular population.

Overall you can therefore see Speckled Wood adults for a total of eight or more months in a year, although any one individual adult probably only lasts a week or so.

Over-wintering is optional in form - either as a caterpillar or a chrysalis, and this is the only UK butterfly species that has this degree of variability in its life cycle. Both choices result in the spring-flying generation, but those individuals that over-winter as chrysalises fly earlier, and those individuals that over-winter as caterpillars fly later.

Females emerge with their eggs only partially mature and usually mate within a few hours. They then have to rest discretely while their eggs develop fully. The eggs are laid singly on clump-forming grasses such as False Brome, Cocksfoot and Yorkshire Fog. The ideal plant is a small isolated grass clump at about 24-30 C, so this is likely to be on the edge of a wood in the spring or autumn, but a shadier and thereby cooler spot inside a wood in the heat of summer.

After the egg has hatched (usually a week to a week and a half) the small caterpillars rest on the underside of the leaf nibbling gradually away at the leaf tissue.

Earlier in the year, pupation takes about ten days for the adult butterflies to emerge.Later, as the year closes down, caterpillars can hibernate in that stage, or pupate, and hibernate in that stage.


Oddities



Predators and parasites

The Ringlet, Aphantopus hyperantus

Ringlet butterflies are not very easy to locate in Hadlow, but these slightly tricky to spot butterflies are a great pleasure to see when you do! The most likely area to find them is along the rides inDene Park.


Description

This delicate beauty is very difficult to pick out from the much commoner Meadow Brown initially, being a bit darker even than the male Meadow Browns. The darkest individuals are fresh males which might seem almost black, contrasting with the white wing edges. However sometimes the best way to spot them can be their behaviour. Dark brown butterflies jinking neatly a few inches over clumps of grass in a slow determined manner might well be the males, looking for females. I haven't seen Meadow Browns doing this in quite the same way. Ringlets will often rest on shrubs, brambles or other vegetation wood edges about a metre up, perhaps with other butterflies such as the Meadow Brown. Ringlets may also be seen competing for access to flowers, such as bramble, thistle and others, feeding off the nectar available.

Although quite early in the flight season, this one, found on its own on the southern edge of Monkdown Wood, Bredhurst, seems to have had a sizeable chunk taken off one of its fore-wings, presumably by a large bird.

 
Distribution

One of the really nice things about Ringlets is the challenge to find and accurately identify them! In Hadlow there is apparently at least one colony within Dene Park, in the small triangles of grass and herbs on the near and far side of the wood from the car park, and along the rides. I have found them there occasionally, in ones and twos in 2011, 2012 (photo below), 2013 and rather more in 2017, for example. I also think there might be some in the privately owned damp grass field to the north of Dene Park, which might be visible from the public access to the edge of the wood.

However, I am sure that I have missed others, and any mix of grass and nearby woodland, scrub and hedge might hold another colony. I would particularly like to check in more wooded edges, larger hedgerows and ditches on the Medway terraces to the South of the Parish. Who knows?

This photo (above) is light enough to be a female or a very worn male.

In the wider UK Ringlets may be found across most parts of the country, except some swathes of NW England and all of the Highlands of Scotland, again particularly in damper grass sheltered from drying out by woods, hedges and ditches. This species of butterfly can also be found across the middle latitudes of Europe and into Asia, with a number of different subspecies.

As a moisture and shade-loving species the Ringlet has increased significantly in distribution and abundance as woods have become denser, shadier and therefore moister over the past five decades. However apart from habitat changes, climate change is thought likely to have a tendency to reduce Ringlet numbers, as summers become on average drier and the chance of summer drought increases. In 1995 the very dry summer reduced numbers of Ringlets temporarily, but the species recovered again over the next few moister years, returning to its gradual upward trend. Could it be that the numbers of Ringlets might be even higher if climate change was not occurring?


Life cycle

The adult butterflies can be found flying from the end of June until the beginning of August, the males perhaps searching doggedly for the females in their characteristic manner. The average life expectancy of an individual male butterfly is in the region of 10 days.

The females invite the males initially, mate once, and then reject further male advances. In this species there are no nuptial gifts donated by the male during mating, and therefore there is no nutritional benefit to the female of mating more than once. Once mated the females squirt out or drop the somewhat triangular initially whitish eggs onto or near grass, possibly in response to chemicals released by fungi infecting the grass, and the caterpillars hunt out suitable infected plants of a particular species of grass to feed on.

The light brownish caterpillars live for about 10 months, hibernating between September and March while still small, until after starting feeding again, they form a little chrysalis in about May from which the adults then emerge. It may be that the adults retain some of the toxins that they absorbed from the fungi in the grass the caterpillars ate.



Oddities

The pattern of spots may be quite varied - it would be very interesting to hear of any odd patterns you might find!

This rather worn individual is showing good visibility of the eyes on its upperwings, but some possible damage to its thorax:

Dene Park, 04-07-2017

This individual though is only showing relatively small dots on its upperwings:

Dene Park, 04-07-2017

Predators and parasites

Lots of birds might have a go at these, despite the assumed content of toxins. Trombidiid mites may infest the butterflies from time to time, infestations lasting for 2-3 days on average. These external mites appear to have little impact on the butterflies abilities to fly and survive.

The Common Blue, Polyommatus icarus

In this butterfly the males have bright blue wings on the upper-sides, while the much more rarely seen females have brown wings on the upper-sides. The males can be seen, flashing a sometimes startling blue, usually flying low on flower-rich grassy areas, particularly reliably on the wildflowers sown on the bank of the reservoir east of Victoria Road, sometimes along a couple of the footpaths neighbouring Common Lane and Carpenters Lane, on College land by the River Bourne when the old permissive path allowed access, in Bourneside Meadow and sometimes in the south of the parish towards the River Medway.

This is the only obvious "bright blue" looking butterfly that most people are likely to see within the boundaries of Hadlow Parish. There are other "blues" that can be found on the Chalk Downland hills to the north of the Kent, such as the Adonis Blue and Chalkhill Blue, but these are restricted to those specialist habitats with their associated caterpillar food-plants. The most easily confused sightings in Hadlow will therefore be light-silvery or duller blue butterflies flying higher, usually around shrubs and trees, the Holly Blue. The undersides of the Holly Blues are a light silver-blue, almost white, while the undersides of both the male and female Common Blues are orange-spotted brown, quite visible at rest once you get your eye in!


Description

The males are generally most obvious and are the most easily seen. Common Blues are about an inch to an inch and a half in wing-span. They are a quite distinctive violet-blue colour as seen from above, as they tend to fly low over the ground, patrolling in search of females, or nectaring. The blue is quite intense on fresh specimens, but tends to fade over time. They quite often seem to "disappear" as they settle, as they close their wings and the blue shape you have been watching is replaced by the entirely different orange-brown of the underside of the wings.

Here is the violet-blue of the upper-wings of a male - notice the unbroken white borders to the wings. This photo was taken at Leybourne Lakes Country Park:

Leybourne Lakes, 

and now the orange-brown of the wings undersides of this male, also at Leybourne Lakes Country Park:

Leybourne Lakes, 

This is a good view of the diagnostic pattern of spots on the underside of the wings. This photo of a male was taken at the Queendown Warren Kent Wildlife Trust reserve. There is a characteristic spot near the body on the under-side of the fore-wing - this is absent in other species such as the Brown Argus. Notice also how the black spots on the under-side of the hind-wing go around the central mark in a very rough circle:

Queendown Warren, 

Female under-wings are similar to the males, but may generally be a little browner in some lights at least. Female upper-wings are generally a lovely but discreet chocolate-brown in colour. This one however, at Queendown Warren KWT reserve, is somewhat faded:

Queendown Warren, 

On occasion you get a "blue-ish" female. Here is a rather tatty female, but showing a degree of blue colouration on the normally brown upperwings, This photo was taken at Trosley Country Park:

Trosley, 

and sometimes you get a really blue female!

Queendown Warren, 30-07-2017

Distribution

Common Blues live in small colonies of perhaps tens (to hundreds in better areas than Hadlow), within which the males are said to hold territories which they patrol to search for females - to me however they often seem to wander fairly randomly, often looking for flower nectar sources. They will also wander away from their home colony areas, either looking for new habitat or just getting lost! The other day one was wandering across my neighbour's lawn - it was a little longer than usual with some hawkbits flowering in it, as he had been away on holiday>

Good places to find Common Blues in Hadlow are many of the long grassy areas, such as Bourneside Meadow, the sunnier parts of footpaths by the old orchard to the west of the cricket field, the banks of the reservoir to the east of Malt Cottage, accessed by the footpath running east from Victoria Lane, the set-aside area alongside Carpenters Lane to the North of Hope Cottage, and some of the wider roadside verges, particularly in the very hot days of early August. It used to be accessible along the old permissive path on the College ground on the other side of the River Bourne to the College dairy.

The early evenings are also good times to check for them, as they often rest quietly with their wings closed, commonly upside down, on grass stems and flower heads, showing the complex and fascinating patterns on the underside of the wings.

The Common Blue is one of the butterflies that likes to roost communally, as shown by this group at Queendown Warren, all lined up to be side-on to the setting sun! Noticed the solitary bee to the right of the group:

Queendown Warren, 

The Common Blue is the commonest "blue" butterfly throughout most of Britain and Ireland, except for the more mountainous areas of Wales and Scotland. It is rarely found above 300 metres. Although it has got to Orkney, it is somewhat less common as you go north, and there may be only one (extended) summer generation (June - September) in the colder wetter conditions of a shorter summer. Abundances do seem to be higher on calcareous and coastal sites in the southern half of the country, but many other warm dry-ish grassland sites where the food plants grow may be used.

The range extends across Europe and temperate Asia as well as into North Africa. It has also recently been accidentally (?) introduced into North America. The habitats used in Europe are even more diverse than the UK, as continental climates appear to permit it to be less choosy about the soil-plant characteristics it requires. It is a very common butterfly in Europe.

Although still widespread and easily found in suitable habitat throughout its UK range, both habitat extent and habitat richness have greatly declined over time with more modern agricultural methods, and overall there are far fewer Common Blues than in the past. Over the last 30 years for which there are data, 90/95 to 00/05) total numbers (measured in UKBMS samples) seem to have decreased by possibly 20%. This decrease is probably also reflected in the populations of the Common Blue in Hadlow.

Life cycle

The larval foodplant is generally claimed to be the Common Birdsfoot Trefoil, Lotus corniculatus, but the Greater Birdsfoot Trefoil, Lotus pedunculatus, and other legumes such as the Lesser Yellow Trefoil, Trifolium dubium and White Clover, Trifolium repens, are apparently also quite acceptable. The caterpillars are green with a green and pale line along their bodies and a tiny black head. They get to about half an inch long when full-grown.

The Birdsfoot Trefoil (and clover) food-plants sometimes contain significant quantities of cyogenic glucosides that are intended by the plant to release cyanide upon cellular damage by predatory herbivores - this works well against unsuspecting (generalist) caterpillars. However specialist herbivores such as the Common Blue larvae contain enzymes that can detoxify the glucosides, and actually use the materials as an extra nitrogen supply, on which they grow faster than if fed upon other plants with no or low cyanogenic glucoside content.

In Hadlow the first adults first appear in the parish about the middle of May, and last until the end of June. There is then a second more populous generation lasting from the end of July until the middle or end of September, and occasionally a small third generation October-ish. The males may perch or patrol in search of females, or be seen flying from one flower to another for nectar. The females are far more difficult to see, creeping about and tapping their feet on plants as they test them for their suitability for egg-laying, placed on the upper surface of young leaves.

The round white eggs after a week or so will hatch into the caterpillars that eat away at the underside of the leaflets, "window-paning" them, until they finally moult into pupae. Both the caterpillars and pupae emit scents and squeaks as they move, thought to be designed to encourage ants (rather rarely noted). The second generation of caterpillars over-winter, before finally pupating the following spring.

The first generation in this habitat often nectars on the Creeping Buttercup, Ranunculus repens, or Field Buttercup, Ranunculus acris, flowers common at that time of year, such as in this photo of a first generation male taken at Queendown Warren KWT reserve:

Queendown Warren, 

However the second generation appears to quite favour the flower heads of the Common Fleabane, Pulicaria dysenterica, which are found then. This is a second generation male nectaring on Common Fleabane at Bourneside meadow, a small patch of undisturbed ground by the side of the River Bourne:

Bourneside Meadow, 

In other habitats, like this one in the Derbyshire Peaks, other flowers such as this Marjoram, are used (Note the red Trombidium mite attached near this individual's head):

Oddities

Populations tend to be highest in years following warm moist summers, but lower in years following hot dry summers, when reproduction is quite badly affected, even if good numbers of butterflies had been seen in the previous year. A positive winter NAO (North Atlantic Oscillation) will also generally encourage better numbers of flying adults in any particular year, particularly through earlier and better emergence of the first generation, as is characteristic of many butterflies with a spring as well as a summer generation of adults.

There are over 43 named variants on the colour pattern in adults that collectors have recognised. One paper suggests that the Common Blue appears to be quite genetically diverse taken as a whole across Europe, but not varying significantly between individual populations. If verified, this could perhaps suggest that the species survived glaciation rather successfully as a large diverse population in Mediterranean regions (with plenty of internal gene flow) that then recolonised the rest of Europe to the north as almost a single unit over the last 12000 years. As always opinions appear to differ as to the interpretation of the facts

Flavonoids from the larval food-plants according to another study appear to be selectively absorbed, retained and stored largely in the adults' wings, and particularly by females. This gender difference might indicate that there is some role for flavonoids in sexual attraction, as well as the other currently suggested roles of UV-protection and antibiosis. Females rich in flavonoids have been shown to be more attractive to males, eliciting more interest from them. This might mean the wings simply appear brighter, or that the flavonoids indicate the better nutrition of the larva - or both.  It also rather begs the question of when, if ever, as a male Common Blue, it is better to cut your losses on a "less-fit" female Common Blue.

Like many other butterfly species, the Common Blue carries an intra-cellular bacterial infection, Wollbachia, passed on via the egg cytoplasm (the maternal line), that appears to be a very unusual symbiont.