Tuesday, 24 August 2010

DRAGONFLY: Ruddy Darters and Common Darters in Lancashire

August 19, 2010:
In this area of north-west England the Common Darter (Sympetrum striolatum) is quite frequent, especially in the lowland areas, but the confusingly-similar Ruddy Darter (Sympetrum sanguineum) appears much more scarce. The Ruddys have moved into the county in fairly recent times and are slowly spreading northwards through Cumbria.

The males of both species are red and quite similar to each other and so also are the yellowish females. Fortunately, both species perch readily and allow a close view to be obtained.

The male Ruddy Darter especially, is perhaps most easily distinguished from the Common Darter (Sympetrum striolatum) in having jet black legs (yellow-striped in the Common), by the presence of a conspicuous black line running down the sides of the frons (absent in the Common), having deep red eyes and frons, a blood-red (not orange-red) more waisted abdomen and a rufus thorax.

[Ruddy Darter, male, both above: the completely black legs, the dark line running down the side of the frons and the deep red eyes and abdomen, can be seen]

[Common Darter, male, both above: the yellow-striped legs, the absence of a dark line running down the side of the frons, the paler more brown eyes and the orange-red abdomen, can be seen]

Ruddy Darters appear to favour sheltered vegetation near choked ditches and pools where the males will perch and often return to the same place if disturbed. Ruddys are also noticeably smaller than Common Darters and are more prone to hover. The Common Darter has a tendency to rest on artificial surfaces as well as on vegetation but this doesn't seem to occur anything like so much with the Ruddy Darter.

Thanks are due to Allen Holmes for helpful discussion on some taxonomic points.

Monday, 23 August 2010

BUTTERFLY: White-letter- and Purple Hairstreaks at Brockholes Wetlands, Lancashire

August 22 (and July 11), 2010:
The first decent weekend's weather for more than a month meant that many butterflies and dragonflies were on the wing on the Reserve. Six weeks ago, I was fortunate to obtain photos (above and below) of White-letter Hairstreaks (Satyrium w-album) there. Since then I had been hoping to get the chance to do the same with Purple Hairstreaks (Neozephyrus quercus). Boilton Wood at the Reserve's northern edge has both of these rather similar-looking butterflies and without doubt merits its SSSI status as a wild-life haven. White-letter Hairstreaks are closely associated with Elm trees (Ulmus spp.), especially Wych-elm, as this is their larval foodplant. Like many Hairstreaks they spend much time high in the tree canopy but will come down for nectar under favourable conditions. On this very warm sunny afternoon in July (the 11th), the weather was ideal, the bramble thickets below the trees were in full flower, and it was there that at least three of them were feeding on the brambles.

Being small, they were most easily located when in flight and needed to be watched carefully to find exactly where they had settled. Unfortunately, the subsequent poor weather appears to have curtailed their reappearance and it may be that this particular colony is only a small, somewhat isolated one. No doubt though, there will be several others elsewhere in these extensive woodlands.

Purple Hairstreaks (photos below) have a later and probably longer flight period. These are found amongst and close to oak trees (Quercus spp.) as this is their larval foodplant and, similar to the White-letter, they fly high in the leafy canopy and are also difficult to locate.

Today (August 22) they could be seen on two separate oak trees in warm but breezy conditions. It is interesting that they occurred in an almost identical situation to that of the White-letters although at a different place along the woodland's edge; they have in fact been seen in at least three separate places here recently.

When looking for both species this summer, even though conditions appeared ideal and the butterflies were known to be present, there were long periods of inactivity with none visible. Patience is needed to locate them.

[Typical habitat of both Hairstreaks, Brockholes]

Wednesday, 18 August 2010

BUTTERFLY: Holly Blues at Silverdale, Lancashire

August 16, 2010:
In brief sunny spells today a small number of Holly Blues (Celastrina argiolus) were flying. This is a site where I have seen them in the past and sometimes also earlier in the season when their larval food-plant is holly. By the month of August any of those flying are of the second generation and, perhaps strangely, the preferred food-plant now becomes ivy. Such behaviour is unknown in other British butterflies.

Here, males and females were associated with a short 50-metre stretch of sheltered, ivy-covered wall but unless it was warm and sunny they only settled briefly. Sometimes they would disappear from the site for long periods but would eventually return when the sun came out.

[Male, both above]


The female differs from the male in having a dark grey border to the upperside of the forewing; in the male this is restricted to just a very narrow band. In the second generation female (as here) these dark markings become more extensive and can extend inwards from the wing edge. In exceptional years there may even be a third generation.

[Warm ivy-covered wall near Silverdale]

Tuesday, 17 August 2010

DRAGONFLY: Lancashire and south Cumbria dragonflies during a brief improvement in the weather

August 15/16, 2010:
Recently in north-west England, the weather has been very poor and there's been an apparent absence of dragonflies. Some warmth and sunshine on Sunday and Monday offered promise, however. At Brockholes Wetlands (Lancashire) on Sunday, many Brown Hawkers (Aeshna grandis) were flying. Unfortunately these never seem to settle enabling a photo to be taken although one female was seen ovipositing onto pondweed (Potamogeton sp) at one of the small pools.

[Brown Hawker ovipositing, Brockholes]

There was also a large number of Common Darters (Sympetrum striolatum) and, in contrast to the Brown Hawkers, these would usually perch accommodatingly. Many Common Blue Damselflies (Enallagma cyathigerum), several Migrant Hawkers (Aeshna mixta), a Southern Hawker (Aeshna cyanea) and an Emperor (Anax imperator) were also seen.

[Male Common Darters, Brockholes]

On an oak tree at the woodland’s edge there were Purple Hairstreak (Neozephyrus quercus) butterflies; these are often elusive and hard to see. Many of the commoner species visited flowers, especially thistles.

[Purple Hairstreak, Brockholes]

At Foulshaw Moss (south Cumbria) on the following day, the main interest was the Black Darters (Sympetrum danae) present in abundance which is often a feature of the site in late summer. Like their Common relative they were also approachable but not so was a solitary Southern Hawker which, although showing curiosity, never settled. Many Common Blue and Emerald Damselflies (Lestes sponsa) active amongst the fringing water plants.

[Pool at Foulshaw]

[Male Black Darters, Foulshaw]

[Emerald Damselflies, Foulshaw]

[Emerald Damselfly, Foulshaw]

Not too far away is the small secluded tarn at Barkbooth. Here an Emperor patrolled the water and there were also two very inquisitive Southern Hawkers and many of the same two species of damselfly as at Foulshaw.

[The small tarn, Barkbooth]

[An inquisitive Southern Hawker, Barkbooth]

Saturday, 14 August 2010

BUTTERFLY: Chalk-hill Blues (Lysandra coridon) at Aston Rowant, Oxfordshire

[Chalk-hill Blue male]

August 11, 2010:
Other than the Silver-spotted Skippers mentioned earlier (see below) there were also many Chalk-hill Blues (Lysandra coridon) flying today. Again, they remained mostly hidden when the sun was obscured but once it returned they were soon in motion and nectaring, especially on the Wild Marjoram (Origanum vulgare) which was in full flower. The males were bright silvery-blue on the upper surface of the wings which contrasted noticeably with the duller brown wings of the females. This butterfly, although restricted to southern Englnd, is much more common than the Silver-spotted Skipper and was very numerous at the site.

[Chalk-hill Blue female, above]

[Chalk-hill Blue male, above]

[Aston Rowant: the short grazed grassland habitat of the butterflies]

The Brown Argus (Aricia agestis), another of the 'blues', was also very frequent here. Both sexes are a rich brown on the upper side of the wings with prominent orange spots towards the outer margin. They also were attracted to the strongly scented Marjoram.

[Brown Argus, below]

Common Blues, Meadow Browns, Small Coppers and Small Heaths were also frequent.

For Silver-spotted Skippers at Aston Rowant today, please see below.

Friday, 13 August 2010

BUTTERFLY: Silver-spotted Skippers (Hesperia comma) at Aston Rowant, Oxfordshire

August 11, 2010:
Following a lack of improvement to the dismal summer weather locally, the forecast for some decent conditions in southern England prompted a day-trip to the Chiltern area to see the Silver-spotted Skipper (Hesperia comma).

This is a relatively rare butterfly in Britain and is at its north-western European limit in southern England. Aston Rowant, close to where the M40 motorway cuts a deep groove through the chalk hill-side, is one of its strongholds and is the most northerly British colony of any size.

This is a late-emerging, single brooded butterfly not on the wing until late July but which then continues to fly throughout August. It is restricted to warm, south-facing slopes on chalk downland where the turf is kept short by grazing and its larval food-plant, Sheep’s Fescue, grows. At Aston Rowant, on the steep warm hillside, there were many small bare patches of chalk presumably exposed by rabbits and it was on these warm areas that the butterfly sometimes basked. However, once the sun went in they would cease to fly but would immediately resume on its return.

[Basking over warm patches of chalk exposed by rabbits]

The butterfies flew fast and low and being of a dull greenish-ochre colour below were hard to follow. However, once settled the prominent silver spots, especially noticeable on the underside of the hind wing, could be seen. The females were darker in colour than the males, the latter having a line of dark scent scales on the forewing similar to some other skippers such as the Large Skipper. A wide range of nectar plants were apparently used but thistles and composites were probably the most favoured. There must be a very large population here as they were regularly encountered over most areas of suitable downland.

[A heavily marked female, above]

Although the most frequent skipper was the Silver-spotted, a few Essex Skippers (Thymelicus lineola) were also seen. These are much more widespread in Britain and nothing like as scarce. The Essex can be distinguished from the very similar Small Skipper by having black tips to the underside of their antennae (rather than brown as in the Small). Also, they have a shorter line of dark scent scales running parallel to the outer edge of the fore-wing, not longer and angled away as in the Small.

[Essex Skippers, showing the black underside to the antennae and characteristic line of scent scales]

Sunday, 8 August 2010

PLANT: Bladderwort at Leighton Moss, Lancashire

August 7, 2010:
Common Bladderwort (Utricularia vulgaris s.l.) is flowering now in some of the fen pools at Leighton Moss Reserve. Bladderworts are very sophisticated aquatic carnivorous plants. They comprise an underwater structure of roots and leaves in the form of long stolons to which small bladders are attached by thin stalks whilst the bright yellow flowers project above the water surface on leafless stems. When flowering en masse as at present, they make a spectacular sight and can be seen from one or two places along the causeway there.

The bladders themselves are active traps in which small organisms such as larvae and water fleas are caught and later ingested by the plant. Each bladder comprises a vacuum possessing a negative pressure so that when small amounts of animal matter brush against its sensitive trigger hairs a trapdoor in the bladder opens and the prey, together with its enveloping water, is sucked inside. The trap then closes within a few milliseconds and dissolution of the prey by digestive secretions begins. A similar species, U. minor, is found in more acidic waters in Cumbria and elsewhere. Bladderworts are members of the Lentibulariaceae family to which the terrestrial Butterworts also belong.