Sunday, 25 July 2010

SPIDER: Raft Spiders (Dolomedes fimbriatus) near Haverthwaite, Cumbria

July 23, 2010:
Raft spiders (Dolomedes spp.) of which only two species occur in Britain and Europe, are the largest spiders we have. Both are rare with the Fen Raft Spider (Dolomedes plantarius) exceptionally so and only known from three well separated U.K. localities. Although more common than the Fen Raft Spider, the ordinary Raft Spider (D. fimbriatus) is still scarce and has a very patchy British distribution pattern. In northern England it occurs only at a few sites in a very limited area of south Cumbria in small acidic pools in raised bogs. These pools may only be a metre or so in extent. Otherwise, the closest sites are in Shropshire.

[Dolomedes fimbriatus near Haverthwaite]

The spiders' bodies can measure over 20mm and, with their legs outstretched, they may cover a diameter of over 70mm; the females are the larger of the two sexes.

Although they can be found on nearby vegetation, being semi-aquatic they are most easily observed at the pools. There they wait at the margins with their rear legs holding onto the vegetation, ready to quickly run across the water surface in pursuit of prey. This is thought to include damselflies, other small insects and even small fishes. If threatened, the spiders will submerge in an instant, the fine hairs covering them helping to envelop them in an air bubble and enabling them to breathe under water.

[The spiders' typical small acidic pool habitat near Haverthwaite]

[Anchored to the vegetation by its rear legs, waiting for prey]

At this site several were seen in the sunny conditions, one of these was smaller and of a paler colouration than the others and presumably a juvenile.

[Juvenile, near Haverthwaite]

Saturday, 24 July 2010

DRAGONFLY: Emperor at Foulshaw Moss, Cumbria

July 23, 2010:
In intermittent late afternoon sunshine at the small pool at Foulshaw, a male Emperor (Anax imperator) restlessly quartered the water.

I watched it for over an hour and it never settled even for a moment throughout this time although on three occasions it successfully chased off an intruding male. Eventually, a female arrived at the pool and then within seconds, after a brief flurry, the pair were settled down in the vegetation. So this was a rare opportunity to get a photo of these mobile insects.


Friday, 16 July 2010

BUTTERFLY: Two subspecies of the Large Heath in Cumbria

July 5 & 8, 2010:
The Large Heath (Coenonympha tullia) is a member of the family of ‘brown’ butterflies which includes the Meadow Brown and Small Heath. It is quite scarce in the UK where it is has a high priority conservation status. In the south of its range it is only found at a few localities in Wales and northern England but is more frequent in Scotland. In Europe it is designated as ‘vulnerable’ and is in decline in many countries.

[subsp. davus, the southern and most strongly marked form with many well-defined eye-spots]

The Large Heath has a specialised habitat requirement: lowland raised bogs, blanket bogs, or damp acidic moorland. Its main larval food-plant is Hare’s-foot Cottongrass (Eriophorum vaginatum). As well as flying in sunshine it can also do so in dull weather provided that it is warm. When feeding on its usual nectar source of heathers, epecially the Cross-leaved Heath (Erica tetralix), it invariably settles with it wings folded so making the upper-sides difficult to examine.

[Typical raised bog habitat of the Large Heath with the yellow Bog Asphodel in the right foreground]

Seen at an acidic bog in north Cumbria in the cool dull conditions pertaining on July 5th, only a few were flying in the more sheltered depressions in the bog but others were well concealed in the heather. The butterfly here is subspecies polydama, so defined by the strength of its wing markings being intermediate between those of the more southern UK localities (subsp. davus) and those of northern Scotland (subsp. scotica).

[subsp. polydama, the less clearly marked, intermediate form from north Cumbria (both above)]

Three days later on July 8th at its classic site at Meathop in south Cumbria, many subsp. davus were flying in breezy but much brighter conditions. This locality and the one seen in the north earlier appear very similar in habitat and vegetation. However, differences in the markings on the butterfly’s underwing are very apparent with those at Meathop showing much more well-defined spots (ocelli) whereas those at the other site (subsp. polydama) have paler wing undersides and fewer, less clearly defined spots. In the far north of Scotland, the underside spots are scarcely visible (subsp. scotica). How clear-cut these subspecies are in reality may be debatable since there seems to be a gradual transition from south to north.

[subsp. davus at Meathop (both above)]

When seen in flight at a distance, it might perhaps be confused with the Small Heath (Coenonympha pamphilus) since the differences in wing-span are relatively slight.

[Small Heath]

Wednesday, 14 July 2010

DRAGONFLY: Keeled Skimmers in Cumbria

June 12-July 13, 2010:
Keeled Skimmers (Orthetrum coerulescens) occur at several places in Cumbria where they particularly favour acidic depressions in mires where there are small runnels of slow-moving water. On June 12 at Outley, only a single newly emerged female could be found, the site being otherwise occupied by Four-spotted Chasers (Libellula quadrimaculata). Two weeks later though, things had moved on and there were now large numbers of both male and female Skimmers flying.

In mid-July, at another site much further to the north in Borrowdale, there were also good numbers of Keeled Skimmers. The vegetation here was comparable to that at Outley with much Bog Bean, Bog Asphodel, Heath-spotted Orchid and Sundew. The Keeled Skimmers showed a degree of curiosity hovering within a metre for several seconds as though inspecting the intruder.

[Habitat: slow flowing runnels in acidic mire]

When settled, the deep golden pterostigma on the wings and the pale ante-humeral stripes on the thorax were clearly visible, whilst the prominent black dorsal keel of the female contrasted sharply with its golden abdomen.

[Male above]

[Female below]

Also flying at the second site were Golden-ringed Dragonflies (Cordulegaster boltonii) and Large Red Damselflies (Pyrrhosoma nymphula).

[Golden-ringed Dragonfly]

Friday, 9 July 2010

BUTTERFLY: High Brown-, Dark Green- and Silver-washed Fritillaries in Cumbria

July 3-8, 2010
In south Cumbria, all three of the larger Fritillaries have now emerged. They are fast-flying, large orange butterflies which inhabit scrub and woodland clearings, especially over limestone, where their bright colouration makes them highly conspicuous. All of them rely on various species of violet for their larval food plant.

Three photos below: High Brown Fritillary:

Two photos below: Dark Green Fritillary:

Two photos below: Silver-washed Fritillary.

When seen in flight these three Fritillaries are difficult to distinguish from each other and even when viewed from above, if perched, they still appear very similar. However, a good view of the underside of the hind-wing makes matters simple. In this respect, the High Brown Fritillary has an additional row of brown, silver-centred, spots (ocelli) lying between the outer margin of the wing and the inner row of seven large silver spots. These ocelli are not present in either the Dark Green or the Silver-washed Fritillary. The High Brown Fritillary also has a brownish tinge to the underside of the hind-wing, whereas in the Dark Green Fritillary it is greenish; in the Silver-washed it is conspicuously silver-banded and almost unspotted.

The markings on the upper sides of the fore-wings also differ, but only slightly. In the High Brown Fritillary the third dark spot (from the wing tip) in the obvious line of spots set inward from the chevrons, is out of line with the previous two whereas in the Dark Green, all are in line. In the Silver-washed, whilst these spots are aligned, they tend to tail off into almost insignificance towards the wing tip. Additionally, the male Silver-washed Fritillary has four very prominent black veins of scent scales on the upper side of each fore-wing.

[High Brown Fritillary (both below), showing the additional ocelli on the under-side and the out-of-line third spot on the upper]

[Dark Green Fritillary (both below), showing the absence of ocelli on the underside and the in-line third spot on the upper]

[Silver-washed Fritillary (both below) showing the prominent silver bands on the under-side and the row of diminishing spots and the male's dark scent veins on the upper]

The High Brown Fritillary is now very scarce in this country with south Cumbria being one of its main strongholds

Wednesday, 7 July 2010

DRAGONFLY: White-faced Darters in Cumbria

July 5, 2010:
White-faced Darters (Leucorrhinia dubia) are rare in the UK and considered threatened, mainly due to loss of habitat. They occur at only a few sites in England although they are rather more frequent in the Scottish Highlands. Their typical habitat is small peaty bog pools with Sphagnum in open acidic heathland.

A recent visit to a site in Cumbria in less than ideal, dull, breezy conditions resulted in at least six separate individuals being seen, most of them males although no doubt there would be many more concealed nearby. In dull light with the sun overcast, they remained hidden near the pools amongst the adjacent heather but as soon as a brief shaft of sunlight appeared, they were active. On this site there are several old, man-made, water-filled peat cuttings and it was at these that they were found.

The males (all photos above) are mainly black with dark red markings on the abdomen and thorax whereas in the females (below) the red colouration is replaced by yellow. Both sexes have a conspicuous white face contrasting with the dark body and from this the common name is derived. They are fast fliers but are more predictable to follow in the air than the Four-spotted Chasers which were also nearby


On one occasion a White-faced Darter settled for a short time on the water surface over submerged Sphagnum as though ovipositing (below) but when viewed more closely it was found to be a male. This seemed rather strange behaviour but perhaps the male was investigating a suitable egg-laying site because in this species very specific requirements for this process have apparently to be met.

The habitat here comprised peaty mossland with a few small pools scattered amongst regenerating conifers with an abundance of heather

Thursday, 1 July 2010

BUTTERFLY: Skippers: Large and Small, Lancashire and Cumbria

June 19-30, 2010:
Large Skippers and Small Skippers are superficially of similar appearance. Whilst the Large Skipper is found throughout most of the country almost as far north as central Scotland, the Small Skipper's northern limit (whilst quite similar) is further south, where it reaches south Cumbria on the west side and somewhat further north on the east. Both species occupy grassy areas, such as meadows, waste ground and roadside verges, and utilise various species of grass as their larval food plant. The males of both species possess a prominent dark line of scent scales on the upper side of the fore wing; this is absent in the females. The Large Skipper is best differentiated from its close relative in its possession of small, almost rectangular, contrasting pale markings, best seen on the upper surface of the wings. The Small Skipper is unmarked in this way and sometimes appears paler overall. It emerges about two weeks later than the Large Skipper. Personal observations suggest that the Small Skipper exhibits a lower, more fluttering type of flight, and appears slighty smaller and paler when seen on the wing compared to the Large Skipper.

Top four photos below: Small Skipper. Lowest two photos: Large Skipper. The dark line of the males' scent scales can be seen on the upper surfaces of the forewings. All shown are males except for the top photo and the right-hand butterfly in the second photo (which are both females).

[Small Skipper (four above), Large Skipper (two below)

[Variously photographed at Gait Barrows and Heysham (Lancashire) and Latterbarrow (Cumbria), June 19-30, 2010]