Category Archives: Insects

Roesel’s Bush-cricket

It’s the time of year when orthopterans are out in force just about anywhere with any decent vegetation. There are four families represented in Britain: grasshoppers are common and familiar; the larger bush-crickets (which many people just refer to as “crickets”) are less conspicuous but still common; then there are the groundhoppers, which take a bit of searching for, and the true crickets, which are just downright rare. This diversity is the reason for going ever-so-slightly jargony with that first sentence: there isn’t really a single good shorthand name, the best compromise probably being “Grasshopper and crickets”.

They are quite an easy group to get to grips with, as there are only about 30 species in Britain, and the species featured in Vic Savery’s photos below is an easy one to identify: the long antennae and chunky body are characteristic of a bush-cricket, and the pale crescent around the edge of the side-panels of the thorax are a dead giveaway for Roesel’s Bush-cricket (Metrioptera roeselii).

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Roesel’s Bush-cricket, 12 August 2013, Avonmouth, Bristol, Vic Savery (naturenutz.net)

When the last national Orthoptera atlas was published back in 1997, Roesel’s Bush-cricket was largely confined to the Home Counties, with isolated outlying coastal populations in a few other areas. However, like a number of other species of bush-cricket, its populations have expanded since then, and it now occurs around Bristol. It is well-established in Wiltshire and Gloucestershire and has also spread into Gwent in the last decade. Robert Cropper’s 2011 book “The Orthoptera and allied insects of Somerset” documents surprisingly few Somerset sites: a strong population around Bridgwater possibly marks the southwestern edge of the current British range, although the range expansion is no doubt ongoing, so I’m sure that the species will reach Devon soon if it hasn’t already.

The song of Roesel’s Bush-cricket is a high-pitched buzzing, pitched at around 22 kHz. If like me, your hearing has deteriorated to the point where you can’t hear sounds which are that high-pitched, you’ll need to use an electronic detector to track one down. Vic tells me there were three or four singing at his site, on Kingweston Lane near Avonmouth. In all likelihood there are other sites elsewhere in the city too.

Beautiful Demoiselles

Vic Savery sent me these excellent photos of Beautiful Demoiselle (Calopteryx virgo), which he took at Three Brooks Nature Reserve in Bradley Stoke yesterday. Demoiselles are our largest damselflies, and one of our most noticable and easily-recognised, and like the Common Clubtail I featured in an earlier post, mainly river-dwelling species.

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Beautiful Demoiselle, 14 June 2013, Bradley Stoke, Bristol, Vic Savery (naturenutz.net)

There are two species of demoiselle in Britain; Banded Demoiselle (Calopteryx splendens), the other species, has a narrow dark patch across the wings in males, with extensive clear areas at both the base and tip, and has a blue rather then blue-green abdomen. Female Bandeds are more similar in appearance to female Beautiful Demoiselle, but with green-tinged rather than brown wings. There are other species of demoiselle in continental Europe, including the Copper Demoiselle (Calopteryx haemorrhoidalis) with a copper-red abdomen.

Beautiful Demoiselle prefers faster-flowing streams with stony riverbeds, whereas Banded likes slower-flowing muddier-bottomed rivers; however the two are often found together, indicating some overlap in the types of river they prefer. Ther British distributions differ: Beautiful Demoiselle is mainly found in Wales, southern and western England, with an outpost in western Scotland, whereas Banded Demoiselle is found throughout England and Wales but only just makes it into southern Scotland.

Around Bristol, both species are found on many of our rivers and streams, including the Avon, Chew, Cam, Wellow, Yeo, and both the Bristol and Bath River Fromes. They are also often found away from rivers (e.g. around ditches on the North Somerset levels, or at ponds and lakes throughout the region).

Common Clubtail on the River Wye

I haven’t featured a dragonfly on this blog yet, so I’m going to remedy that now with a rather good one. This is a female Common Clubtail (Gomphus vulgatissimus), photographed by Martyn Hall next to the River Wye at Monmouth yesterday.

Club-tailed Dragonfly
Common Clubtail, 9 June 2013, River Wye, Monmouthshire, Martyn Hall (www.martynhallphotography.com)

The river here is a well-known site for this species, and with the good weather today, Martyn & I thought we’d give it a try. We walked north-east up the west bank from the Wye Bridge, and eventually found this individual on a stretch of the river to the north of St Peter’s church, at this location:

Older books just call this species the “Club-tailed Dragonfly” but there are several other closely-related species in Europe that this name could apply to, and this is the one with the widest range, hence the newly-coined name. In Britain, however, it’s not common at all, being confined to just eight river-systems. As well as the Wye, it’s found on the Severn, reaching downstream as far as Tewkesbury, on the Thames in Oxfordshire, the Lugg in Herefordshire, the Dee in Cheshire, the Arun in Sussex and two rivers in west Wales, the Teifi and Tywi. A slow water flow, lack of pollution, a silty river bottom, plenty of bankside vegetation and nearby woodlands are all essential habitat requirements, which explains the restricted British range.

Common Clubtail has quite a short flight period, but should be on the wing here for a few more weeks. After emerging in May, they leave the river to feed in surrounding woodlands and then return to set up territories, so numbers on the river may not yet be at their peak given the late spring. There were also around 20 Banded Demoiselles (Calopteryx splendens), but no other dragonflies on this visit, although this site does also have White-legged Damselfly (Platycnemis pennipes) later in the season.

Dingy Skippers on Cleeve Hill

The Bill Smylie butterfly reserve, on the western slopes of Cleeve Hill, the highest point of the Cotswolds, is somewhere I’ve been meaning to visit for a while. As it looked like very good butterfly weather yesterday, I decided to give it a go, There was no sign of any Duke of Burgundy butterflies, the species for which the site is best known, but several other species were present: Dingy Skipper (Erynnis tages) was the most numerous species, and I managed a number of half-decent photos.

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Although Dingy Skipper is widespread in central and southern England, it tends to be confined to fairly good-quality sites. Its caterpillar feeds on Bird’s-foot Trefoil (Lotus corniculatus) and other related species in the pea family. Bird’s-foot Trefoil is a common species in limestone grassland that hasn’t been agriculturally “improved”, and it’s in these sites that Dingy Skipper does best, although it also occurs in patches of open habitat within other sites, e.g. woodland rides and clearings, particularly if there are bare open patches where adult can sunbathe. There are strong populations on the Cotswolds and the Mendips, however it is a species which is in decline. In the 1970s and 80s, it was found at several sites in and around Bristol, but no longer occurs here. It is possibly still found on the east edge of Bristol, near Rodway Hill, although the last records here on the National Biodiversity Network website are from 1998.

Dingy Skipper could be overlooked as a moth due to its dull colours: in fact there are several species of day-flying moth which look similar, such as the Burnet Companion (Euclidia glyphica). In fact, in evolutionary terms, butterflies are just a specialised day-flying group buried deep within the moth evolutionary tree. Skippers have in the past been thought not be closely related to the remaining butterflies, although DNA studies from the last decade show that this isn’t the case, and that all butterflies, including the skippers, arose from the same common ancestor, and that no moths evolved from this ancestor (in biological jargon, butterflies are ‘monophyletic’).

Bill Smylie reserve is a few miles northeast of Cheltenham, on the edge of the minor road that leads up to Cleeve Hill common:

Yellow-barred Brindle

Yellow-barred Brindle

This is a Yellow-barred Brindle (Acasis viretata), which I found sitting on (rather than in) my moth trap this morning. I’ve not been running the trap much yet this year: many nights have just been too cold, and on the warmer nights when I have run it, it has pulled in very few moths. Hopefully this should start to change soon, and I can add more moth-related posts.

Yellow-barred Brindle is quite a widespread moth, occurring in woodlands, gardens, and areas with hedgerows, but in my experience only tends to turn up at moth traps in low numbers; I’ve only ever trapped single individuals here. In the south of England it is bivoltine, i.e. there are two generations per year: adults emerge in May to June, and then again in September to October. Unlike some moths, it’s not particularly choosy over its larval foodplant: many common shrub species are suitable.

It’s a member of the Geometridae, the second most species-rich family of larger moths in Britain. Almost all moths in this family hold their wings flat at rest, and many of them hold them back in the distinctive upside-down heart shape which this Yellow-barred Brindle is resting in. Some moths in other family have simiar resting positions, but you’ll be correct 9 times out of 10 if you narrow your search to the Geometridae when faced with an unidentified moth that looks like this. There are relatively few moths that are bright green in colour like Yellow-barred Brindle, so that helps the identification process enormously. Note though that the green colour is at its most intense in fresh specimens and fades to yellow quite quickly.

There are two excellent websites which contain large collections of photos of British moths: UKMoths and UK Lepidoptera: see the Web resources page for details.

Helophilus pendulus

Helophilus pendulus for blog

Helophilus pendulus is one of Britain’s commonest and most widespread hoverflies, found around fresh water pretty much anywhere. Several of these have been present at the ponds in our garden in the last few days, and the species will probably be present all summer. Like most hoverflies, it doesn’t have an English name (yet),

In hoverflies, the sexes can usually be told apart easily, as males have their eyes touching on the top of their head, whereas females don’t. Helophilus is an exception: males and females have their eyes separated.

Helophilus hoverflies can be told apart from most other groups of hoverflies found around Bristol by the pronounced longitudinal yellow stripes on the thorax. Two other species of Helophilus are also found locally: H. hybridus is scarcer; males don’t have the narrow black band across the middle of the abdomen (leaving clear yellow panels running down each side). H. trivittatus is bigger, with paler yellow areas, and can be quite common in late summer when numbers are swelled by migrants. When seen close-up, both species have other useful identification features: a very good photographic identification guide to hoverflies – Britain’s hoverflies: an introduction to the hoverflies of Britain, by Stuart Ball and Roger Morris – was published recently and gives much more detail on how to tell these species apart.