Sunday, 27 June 2010

DRAGONFLY: Beautiful Demoiselles (Calopteryx virgo) in Cumbria

June 24 & 26, 2010:
These spectacular dragonflies are relatively scarce in northern England and usually found near to vegetation bordering fast-flowing streams.

Cumbria, however, has several localities. At this site in the south of the county, the stream is distinctly sluggish and really little more than a wide dyke passing through agricultural land. However, the banks had extensive fringing beds of vegetation (Phalaris arundinacea) amongst whose roots the larvae would have developed and on which the emerging insects often perched.

Even over just a 30 metre stretch of stream, at least six males were present but no females were seen, presumably not having emerged yet. Upstream and downstream there would no doubt be many more Demoiselles.

Their slow fluttering flight and bright metallic-green bodies seemed almost surreal in the bright sunlight. Males often approached each other very closely but never seemed to show hostility, quite different from many other species of dragonfly. Swallows occasionally skimmed over the stream so that the detached wing of a Demoiselle found in the water suggested that they are sometimes taken as prey.

[View upstream and downstream from the site showing the abundant fringing vegetation. Thanks to Bill Gregory for details of the locality]

Wednesday, 23 June 2010

BUTTERFLY: Silver-studded Blues at Whitchurch, Shropshire

June 22,2010:
The continuing hot sunny weather provided an opportunity to visit the only locality in England other than in the south for this butterfly. The site at Prees Heath is open common heathland where conservationists have done much work in supporting the butterfly.

Prees Heath lies between two Roman roads and has many historical connections. The area was once used as a Bronze Age burial ground whilst for many years a gallows was established there and was the site of one of the last public hangings in England. In the thirteenth century it was a muster point for King John's army when he invaded Wales and later it was used by Prince Rupert for the same purpose in the Civil War. During the twentieth century's two World Wars there was further military activity as an airfield, a training ground, and an internment camp.

The whole heath is flat and in those places where the butterfly if found is covered with light scrub and heather (the larval foodplant). Silver-studded Blues are in evidence from mid-June into July and on this occasion, in the warm sunny conditions, up to ten could be seen in flight at the same time.

[Taking nectar from heather flowers]

The butterfly's name derives from the small silver 'studs', actually bluish, present inside the black spots towards the edge of the under side of the hind wing. In some butterflies most of the spots are studded, in others just a few. The upper side of the wing has a pronounced dark margin. The males are bright blue but the females are duller and often brownish.

[The silvery-blue 'studs' are visible in the photo]

[Female low down in the vegetation searching for an egg-laying site]

Monday, 21 June 2010

DRAGONFLY: Emperors (Anax imperator) at Brockholes, Lancashire

June 20, 2010:
A warm and sunny Sunday morning appeared promising for dragonflies so a walk round some of the more remote pools at Brockholes with Allen Holmes seemed likely to produce good results. A stiff breeze from the north-west at first kept numbers down but later when this subsided, several species were seen. Perhaps of greatest interest was the presence of at least seven male Emperors distributed over three of the smaller pools. All had clearly defined territories and immediately drove off approaching males as well as the frequent Black-tailed Skimmers. The Emperors flew very quickly but at one stage, and quite unusually, a male settled on a bank giving a rare opportunity for a photograph.

A female Emperor could be seen ovipositing on submerged water-weed towards the middle of one of the pools, remaining stationary for a while and bending and inserting its lower abdomen into the water, occasionally buzzed by a male Black-tailed Skimmer.

[Emperor ovipositing, buzzed by a male Black-tailed Skimmer below]

On another occasion a female Broad-bodied Chaser also oviposited but used a different technique to the Emperor, very briefly dipping and trailing its abdomen over the water surface, moving on all the time, and attended and protected throughout by a male.

[Broad-bodied Chaser ovipositing, male above]

Common Blue and Blue-tailed damselflies, Four-spotted Chasers and a single Banded Demoiselle were also seen as well as Small Tortoiseshell and Large Skipper butterflies. Thanks to Allen whose sharp eyes spotted the perched male Emperor (and much else).

[Black-tailed Skimmer, male]

Thursday, 17 June 2010

BUTTERFLY: Small Blue, Maryport, Cumbria

June 16, 2010:
In England, the Small Blue (Cupido minimus) is very scarce north of a line from the Severn/south Wales to the Wash. At one time it was thought to be extinct in Cumbria, not having been seen there for more than a decade until I had the good fortune to find a surviving colony at Maryport in early July 1983 (Entomologist's Record (1983) 95: 248-9). Since then, the colony seems to have thrived and additional populations have been found in the same general area.

As its name implies the butterfly is much smaller than other British blues with a wing span of about 20 mm. Their territories are very small, often only 20 metres or so in extent and only occur where their larval food-plant Kidney Vetch (Anthyllis vulneraria) is frequent.

Small Blues fly quickly and very close to the ground and this, together with their grey-blue colouration and small size, makes them difficult to follow. They especially favour small sheltered banks and depressions which are warmed by the sun. This particular population occupied perhaps a mere 25 metres long section of a steep sunny bank with much Kidney Vetch present. There were probably 15-20 butterflies flying here at the time, a few having become worn, although others appeared freshly emerged.

Here, the Small Blue flies from June to early July, the later ones probably resulting from a second brood. Eggs are laid individually onto separate flower heads and the larvae, which are cannabilistic, burrow into the calyxes and eat the seed. When fully developed they descend to ground level and, in a similar to those of the Large Blue, are thought to be attended by species of ants as they over-winter in soil crevices.

[The warm sunny bank, the habitat of this Small Blue colony]

Common Blues, Large Skippers and Meadow Browns were also flying here in the bright sunshine.

Sunday, 13 June 2010

BUTTERFLY: Small Pearl-bordered Fritillary, Haverthwaite, Cumbria, and a comparison with its close relative

June 12 & 15, 2010:
A colony of Small Pearl-bordered Fritillaries was found on very boggy, acidic ground near Haverthwaite where the butterflies were frequently nectaring on bog-bean (Menyanthes trifoliata). This butterfly is usually found in open woodland and scrub, often over limestone, where its food-plant, various species of violet, commonly grow. Therefore, this unusual site was in strong contrast to its normal one. Small Pearl-bordered Fritillaries are much commoner than the close related, scarce, and now threatened Pearl-bordered Fritillary which flies earlier from May onwards, although their flight periods do overlap.

[Small Pearl-bordered Fritillary: upper side. Very similar to the Pearl-bordered Fritillary, below]

[Small Pearl-bordered Fritillary: underside. The additional silver spots, the dark chevrons, and the large central spot, all on the hind wing (see notes below) can be clearly seen]

Viewed from above the two species are very difficult to separate even when at rest but if the undersides of their hind wings are examined the differences become apparent. In the Small Pearl-bordered Fritillary, there are several additional central silver spots as well as the seven on the wing margin (there are only two bright central spots on the Pearl-bordered), the outer spots are outlined with dark chevrons and the adjacent line of dark spots is bold (this is not so in Pearl-bordered), and also there is a large black-margined central spot in the Small Pearl-bordered but this is almost insignificant in the other species. Compared with the male Small Pearl-bordered Fritillary, the female has more rounded wings, a broader body, and is more heavily marked.

See below for the Pearl-bordered Fritillary's upper- and under-sides as photographed at Gait Barrows recently.

[Pearl-bordered Fritillary, upper-side. Very similar to that of the Small Pearl-bordered Fritillary]

[Pearl-bordered Fritillary, showing its differently marked under-side]

Thursday, 10 June 2010

DRAGONFLY: Red-veined Darter (Sympetrum fonscolombii) at Asprokremnos, Cyprus.

May 8, 2010:
At the Asprokremnos pool, as well as there being many Purple Drop-wings, some Red-veined Darters were also present.

The male photographed here shows the characters of this species: a red venation in the wings, prominent black lines bordering the pterostigmas, the abdomen with black marks on the rear dorsal segments, and the abdomen itself narrowing strongly after the second segment. Not visible from the photograph is the blue colouration of the bottom part of its eyes.

It is a widespread resident of the Mediterranean area including Cyprus and also a strong migrant which reaches Britain in most years. I'm grateful to Allen Holmes and Yiannis Christophides for their comments on this photo.

Sunday, 6 June 2010

BUTTERFLY: Marsh Fritillary at Finglandrigg, Cumbria (a conservation success)

June 5, 2010:
At one time there were more than 200 colonies of the Marsh Fritillary in Cumbria but the number subsequently declined quite rapidly. I can recall seeing just a few butterflies at each of three or four surviving colonies in the early 1980s but by 1995 only one colony remained. There, the butterfly lingered on for a few more years but by 2004 it was considered to be on the point of extinction and so drastic action was carried out by the local butterfly Action Group. They took the surviving eggs into captivity and the emerging butterflies were bred on in various ways (in some cases involving strains from other UK localities) with the object of re-introducing the resulting progeny to a few of the old Cumbrian sites. This has now been successfully completed so that at Finglandrigg NNR (near Carlisle) and at a few other sites, the Marsh Fritillary is re-established.

[Perched by a leaf of its food plant, Devil's-bit Scabious]

[Underside view with the light shining through]

The cause of decline is not fully understood but as the butterfly’s specialised habitat became overgrown due to changing agricultural practices, only a few small isolated colonies survived. This resulted in a classic case of population collapse due to inbreeding, the genetic diversity within these small colonies having been lost.

The Finglandrigg site comprises a large marshy pasture lying in a shallow valley bottom where the butterfly’s food plant, Devil’s-bit Scabious (Succisa pratensis), is abundant. In warm sunny weather today, there were dozens of Marsh Fritillaries flying and the whole site must have held hundreds. Small Heaths were also present, again in large numbers.

[The site at Finglandrigg with a lepidopterist photographing a Marsh Fritillary]

This re-established site is an excellent example of what can be achieved by nature conservation. The successful re-introduction of the Lady’s Slipper orchid to south Cumbria is another.

[A Marsh Fritillary with a deformed right hind-wing which had difficulty flying. Could this result from an inherited genetic defect passed down from its small ancestral population?]

Thursday, 3 June 2010

BUTTERFLY: Skippers at Wrexham

[Large Skipper]

June 3, 2010:
The continuing sunny weather is ideal for butterflies. One species which should be flying now and which reaches its northern British limit in Denbighshire is the Grizzled Skipper. Known to occur in that county only in small numbers, it nevertheless seemed worth taking the chance to try to find it in the present good conditions. Loggerheads Country Park near Mold is a known locality and was checked first but today none could be found although one had been reported 'last week'. So, a move to a second known locality near Wrexham (Wrecsam) was called for. This was a 'brown field' site on an industrial estate with suitable habitat covering only a very small area. Again, no Grizzled Skippers were found on what is a very flower-rich piece of grassland but Dingy Skippers and Large Skippers were present as well as Small Heaths and Common Blues.

[Dingy Skipper]

[Dingy Skipper]

[Common Blue]

[Small Heath]

This site at Wrexham is becoming rather overgrown and there was little evidence of the presence of the Grizzled Skipper's food plant (Wild Strawberry). A disused quarry nearby at Marford was also checked. Here there was abundant food plant but again no Grizzled Skippers could be found.