Glasgow & SW Scotland Butterflies

Glasgow & SW Scotland Branch Website

April 24, 2009

Pick of the Week 2

Filed under: Moths — Tags: , , , — Heather Young @ 10:49 am

The weather has not been terribly conducive to bumper hauls in the trap over the last couple of weeks, with several quite sharp frosts (compensated for by some stunningly nice sunny days), but there have still been a few Common Quaker (Orthosia cerasi), and Hebrew Character (O. gothica), accompanied by a couple of Brindled Pugs (Eupithecia abbreviata), an Early Tooth-striped (Trichopteryx carpinata) and an Engrailed (Ectropis bistortata).

For this ‘Pick of the Week’ however, I am going to encourage you to venture out into the countryside in search of one of our most spectacular moths, the Emperor (Saturnia pavonia). You may not have to go too far; many towns have a local ‘moss’ retaining some good quality habitat, although much of it has disappeared in recent years under housing developments in our branch area.
 

On the wing during April and May (although I have seen one at the end of June in Lochaber), the males fly during the day, and restlessly patrol the area searching for females. They fly very rapidly, and are often mistaken for butterflies, but don’t seem to settle and bask in the sunshine like peacocks and small tortoiseshells, making them extremely difficult to admire at close quarters! One sunny afternoon at the weekend on my local heath, after half an hour of what must have been, to the casual onlooker, highly amusing antics with a net, I eventually succeeded in capturing one to confirm identification. Unfortunately, he just would not sit still and pose for a photograph like the far more co-operative individuals that populate the egg trays in my trap at the moment, so I set him free to resume his quest, and borrowed some pictures of a newly-emerged male (with the orange hindwings) and female which had been bred from larvae: 

© John Bebbington, FRPS (Secretary, Somerset Moth group)

© John Bebbington, FRPS (Secretary, Somerset Moth group)

© John Bebbington, FRPS (Secretary, Somerset Moth group)

The female is a much better bet for observing in the wild, as she flies at dusk, and can sometimes be found at rest on vegetation before the light fades. She will also come to light, so why not try taking a portable trap if you have one, or a torch and sheet if you don’t, and see if you can tempt one to come to you. Females will lay eggs on just about anything if they do end up in the trap, and larvae can be raised on bramble, heathers or sallows if you fancy giving it a go. If you do, please remember to release the adults back where you found them the next year (unless a new housing estate has sprung up in the meantime, in which case the nearest suitable habitat).

 

Later in the spring and summer, have a look for the caterpillars – these ones were photographed near Fort William in late June, feeding on the shoot tips of heathers in the perpetual drizzle of a Scottish summer. Each instar, or stadium, of the larva is a little different (these are quite well developed), culminating in a large, fat, green caterpillar with black hoops and yellow or pink warts with little tufts of hair sprouting from them.

 

   

 

 

 

 

Emperor moths are not rare, and are widely distributed across the country in suitable habitat, but for such a spectacular creature, are surprisingly often overlooked: let us know using the comments facility if you manage to find any near you.

 

My thanks to John Bebbington for allowing me to use his excellent photographs.

 

Heather Young

March 7, 2009

Definitions of Grassland Habitats for Conservation Management

Grassland Habitat categories using Phase 1 Habitat Survey Descriptions

When reading descriptions of species habitat preferences and reviews of conservation techniques, I’ve often wondered how ‘experts’ tell different types of grasslands apart. This can be important in defining the specific habitat conditions required for the conservation of our endangered native butterfly and moth species.

The following definitions are taken from the Handbook for Phase 1 habitat survey methods published by the Joint Nature Conservation Committee. A phase 1 habitat survey is a technique used by environmental consultants and others interested in auditing environmental characteristics of a location to assess conservation values. For images of some of the species mentioned see http://www.floralimages.co.uk/.

Most grasslands have been subjected to some degree of agricultural improvement by repeated grazing, mowing, fertilising, drainage or herbicide treatment.  It is important to try to distinguish unimproved and semi-improved from improved grasslands. However, these types of grassland often for a continuum so that it is not normally possible to define each with precision, especially as species critical for definition are often only observable for a short season of the year.

Agricultural improvement usually results in a decrease in floral species diversity of the sward and dominance of a few quick-growing grasses such as Perennial Ryegrass (Lolium perenn), Yorkshire Fog (Holcus lanatus ) and Red Fescue (Festuca rubra). The resulting sward composition is likely to vary  with intensity of treatment, so careful observation and field work is often required to define and maintain boundaries between these categories.

Calcareous Grassland Thyme and Rock-Rose

Calcareous Grassland Thyme and Rock-Rose

Unimproved Grassland

Unimproved grasslands are likely to be rare in lowlands. They may be rank, neglected, mown or  grazed. They may have been treated with low levels or farmyard manure in the past, but should not have had sufficient applications of fertiliser or herbicide, or have been intensively grazed or drained so as to alter the sward composition significantly. Species diversity is often high with species characteristic of the area and soil type with a low percentage of agricultural species.

Semi-improved Grassland

Semi-improved grassland is a transition category made up of grasslands which have been modified by artificial fertilisers, slurry, intensive grazing, herbicides or drainage and consequently have a range of species which is less diverse and natural than unimproved grasslands. Such grasslands are still of some conservation value. Semi-improved grasslands may originate from partical improvement of acid, neutral or calcareous grassland. Often the improvement of the site can reduce the distinctive characteristics of acid or calcareous grassland, so that this is not always easy to distinguish in the field. Species diversity will generally be lower than in unimproved grassland in the same area. If key signs of improvement are missing (see below), then the grassland is likely to be semi-improved.

Improved Grassland

Improved grasslands are those meadows and pastures which have been so affected by heavy grazing, drainage or the application of herbicides, inorganic fertilisers, slurry or high doses of manure that they have lost many of the species which one could expect to find in an unimproved sward. They have only a very limited range of grasses and a few common herbaceous flowering plants, mainly those demanding of nutrients ands resistance to grazing. Perennial Ryegrass (Lolium perenne), Crested Dogstail (Cynosurus cristatus),  White Clover (Trifolium repens), Common Sorrel (Rumex acetosa) Dandelion (Taraxacum officinale) Daisy(Bellis perennis) Meadow Buttercup (Ranunculus acris) and  Bulbus Buttercup (Ranunculus bulbosus) are all typical of improved grassland, while stands of dock (Rumex species), common nettle (Urtica dioica) and thistles (Cirsium Species) indicate local enrichment of the soil by grazing animals.

The following signs usually indicate substantial improvement:-

i) Bright Green, Lush and even sward, dominated by grasses

ii) Low diversity of herbaceous flowering plants

iii) More than 50% Perennial Ryegrass (Lolium perenne), White clover  (Trifolium repens)  and other agricultural species.

Fields which have been reseeded in the past and have since become somewhat more diverse are included in this category, but recently seeded monoculture grassland such as ryegrass leys and fields of arable crop species are classified as Cultivated Land.

Small Pearl-Bordered Fritillary on Ragged Robin

Small Pearl-Bordered Fritillary on Ragged Robin

Acid Grassland

Grassland in this category is often unenclosed. As on hill grazing land and occurs on a range of acid soils (pH less than 5.5). It is generally species poor and often grades into wet or dry dwarf shrub heath, although it will have less than 25 % dwarf shrub cover (see Heath definition below). Pioneer annual-rich calcifuge (alkaline-intolerant) communities on dry sandy soil are included in this category, as are wet acidic grasslands typified by species such as Heath Rush (Juncus squarrosus). The following species are indicative of acidic conditions when frequent or abundant:Wavy Hair-Grass (Deschampsia flexuosa), Mat Grass (Nardus stricta), Heath Rush (Juncus squarrisus), Heath Bedstraw (Galium saxatile) and Sheep’s Sorrel (Rumex acetosella).

Neutral Grassland

Typically enclosed and usually more intensively managed than acid or calcareous grassland (except on roadside verges), this category encompasses a wide range of communities occurring on neutral soil (pH 5.5-7.0). The following are indicative of neutral conditions when frequent or abundant: Meadow Foxtail (Alopecurus pratensis), False Oat-grass (Arrhenatherum elatius), Crested Dogstail (Cynosurus cristatus), Cock’s Foot (Dactylis glomerata), Tufted Hair-grass (Deschampsia cespitosa), Tall Fescue (Festuca arundinacea) and Meadow Fescue (Festuca pratensis).  Perennial Ryegrass (Lolium perenne) may be present, but when abundant it is indicative of improved grassland.

Hay meadows will usually fall within this category. After cutting a hay meadow can have the appearance of improved grassland as the new growth comes through. Included in neutral grassland is a range of grasslands which are inundated periodically, permanently moist, or even water-logged. Some examples include: Water meadows, alluvial meadows and Wet pastures where grasses are dominant but with species such as Marsh Marigold (Caltha palustris), Meadow sweet (Filipendula ulmaria), Valerians (Valeriana species), Rushes (Juncus species) or Marsh Hawksbeard (Crepis paludosa ) present.

Calcareous grassland

These grasslands are often unenclosed, not managed intensively and occur on calcareous soils (pH above 7.0). Mountain avens (Dryas octopetala) communities are included. Where grass is tall the dominant species is usually either Drooping Tor-grass (Brachypodium pinnatum) or Upright Brome (Bromus erectus), whilst species indicative of short, close-grazed and species-rich calcareous turf are Crested Hair-grass (Koeleria macrantha), Downy Oat-grass (Avenula pratensis), Blue Moor-grass (Sesleria albicans), Common Rock-Rose (Helianthemum nummularium), Salad Burnet (Sanguisorba minor), and Wild Thyme(Thymus polytrichus).

Other definitions

Heathland is classified as being dominated (greater than 25 %) by heathers or dwarf gorse species. 

Scott Shanks

 

January 7, 2009

A second brood of the Iron Prominent in the Glasgow area?

Filed under: Moths — Tags: , , , , — Scott Shanks @ 12:34 am

The Iron Prominent (Notodonata dromedarius) is a furry medium-sized moth with distinctively marked dark grey-brown forewings with rusty-brown streaks.  According to Waring & Townsend, the species is widely distributed throughout the UK, however the distribution map on the NBN gateway site suggests it’s largely absent from south west Scotland. Individuals in northern England and Scotland often have a darker ground-colour with fainter markings.

Iron Prominent on my thumb

Iron Prominent on my thumb

In the south of Britain there are usually 2 generations per year, with adults flying in May-June and late July-August, while in the north of Britain and Ireland there is a single generation each year with adults flying June-July…at least that’s what it says in the books!

While trapping at SWT Loch Ardinning (Just north of Glasgow) on the 30th of August 2008 I had an Iron prominent come to the light of my 15W actinic heath trap. (NS569777 ). It was a feisty wee thing and took ages to settle down, causing total havoc as it disturbed the other moths in the trap. I think that’s why one of its wings looks so badly worn.

Iron Prominent moth

Iron Prominent moth

 

 I passed this record to John Knowler the vice county moth recorder for Stirlingshire, who replied had he’d also had a late Iron prominent come to light.  It looks like the Iron prominent may have had a partial second brood in Scotland during 2008.

Could this be a response to global warming? According to BBC weather records for 2008, temperature records in Scotland were a degree or two above average during both July and August. It was also wetter than usual once more! Could it be that this small increase in temperature is enough to trigger a biochemical response in larvae or pupae that aborts the usual ‘hibernate’ signal, and leads to accelerated development of larvae or early emergence?  

The Iron prominent can be found in broadleaved woodlands, heaths, wet carr, riverbanks and occasionally gardens. The pale green caterpillar has a brown stripe along its back, with humps on the 4th-7th and 11th segments of its body. It can be found feeding on birch and alder, and occasionally hazel or oak. The Iron prominent overwinters as a pupa in a flimsy cocoon under the soil. Supposedly the caterpillar is quite easy to raise in captivity if supplied with fresh vegetation every few days, but should probably be returned to the wild before it pupates to maximise the chance of the adult’s emergence coinciding with a suitable mate the following year.

Certain montane invertebrate species can exhibit delayed larval development in cold and wet years, which prevents the population being wiped out if the adults emerge during inclement conditions and fail to breed. The ability to produce additional generations when conditions are good may be another aspect of this phenomenon?

Does anyone else have other ‘late’ records of the Iron prominent in Scotland? Was this a local event or was it nationwide? It’s likely that other species may be responding to temperature increases in a similar way. Perhaps we could compile a list of species that are taking advantage of climate changes to produce further generations during the year? Such species may prove useful as biological indicators of wider habitat and environmental changes happening around us that we should ‘keep an eye on’ in the future.

Feel free to add any sightings, comments or thoughts below. :)

Scott

Powered by WordPress