Monday, 9 July 2018

Last orders please …

Purple Emperor (Apatura iris)

Knepp Estate, West Sussex (5th and 6th July 2018)






The 2018 Purple Emperor season has all but come to an end. My first sighting this season came on Tuesday, 17th June, with several sightings in the traditional areas of Chiddingfold Forest, Surrey. The first Sussex specimens appearing a few days earlier.

The varied and sometimes rather offensive feeding behaviour of iris has always fascinated me. Putting aside the rather unpleasant nature of male table manners, both male and female iris will travel some distance to major sap runs on trees.

A tree, by its very nature, is a closed hydraulic system. Water rises up through the tree in the outer edge of the woody material; the xylem. The water, which is called sap, is a solution of mineral salts that have been absorbed from the soil. The sap is enriched with sugars being transported from storage in the roots to the shoots where they are used to provide energy necessary for shoot growth and leaf expansion. Once there is positive water pressure in the tree, damage to the tree may release the pressure and allow sap [usually a colourless watery liquid] to escape and the tree will 'bleed'. Alcoholic flux is a stress-related disease. It usually occurs after a period of very hot, dry weather. The disease is caused by a microorganism that ferments the sap that seeps or bleeds from cracks and wounds in the bark. The result is a white, frothy ooze that has a sweet, fermenting odour similar to beer. Anyone who has ever sugared for moths will know how effective a mix of molasses and beer can be in attracting a host of insect species; the odour of fermenting sap having a similar appeal.

The above images show iris feeding on several oak sap runs high in the canopy.

More at:

Patch, D. (2004). Trees Bleeding. Trees in Focus, Arboricultural Practice Notes (APN 8). Farnham: Arboricultural Advisory and Information Service.

Monday, 2 July 2018

Next time …

Purple Emperor (Apatura iris)


I thought I was going to get really lucky this morning having come across a male and female iris, on the ground and within one metre of one another, and it was only 8.45am. I of course had high visions of courtship and a mating pair. Sadly, the male was more interested in what a dog had left behind than the pristine female behind him. By the time he’d had his fill she had already departed into the canopy no doubt looking for a more appropriate suitor.

More at:

Friday, 29 June 2018

Heatwave ...

Purple Emperor (Apatura iris)



2018 is turning out to be an excellent year for the Purple Emperor in my local woodlands. My first official sighting this season came on Tuesday, 17th June, with several sightings in the traditional areas of Chiddingfold Forest. Numbers have been steadily building and on Monday, 25th June 2018, I counted at least 25 separate males and had multiple sightings of many individuals. It has also been a good year for iris aberrations with at least three ab. afflicta (Cabeau, 1910) being observed to date; the first found by Jan Wilczur on the 25th June.

The current heatwave has meant that the best time to see grounded males is early morning; the earlier the better. By early-mid-morning, when all remnants of any early moisture have evaporated, the males have been observed flying low over the woodland tracks and, when not searching the sallows for females, nearly always alighting in areas of shade where they actively try to extract minerals from the parched ground. Both sexes can also be found feeding from sap runs though these can be difficult to locate. By midday, both sexes, probably due to the extreme temperatures, have been resorting to their arboreal home where they bask in the shade - I can’t say I blame them.

More at:

Wednesday, 6 June 2018

Spirit of the oakwood …

Small Pearl-bordered Fritillary (Boloria selene)



A visit to the Ardnamurchan peninsula at any time of year is always a great pleasure but in early June it becomes a very special place. Ariundle National Nature Reserve near Strontian is one of the many jewels in the stunning Scottish landscape and it is here, observing gems such as the Small Pearl-bordered Fritillary Boloria selene, that one can truly feel at peace with nature. Time your visit well and patrolling males can be seen flying a short distance from the ground, alternating a burst of rapid wing beats with a short glide, searching out freshly-emerged females hidden amongst the vegetation surrounding the beautiful Strontian River.

The strongholds of B. selene are located throughout much of Scotland and Wales, and in the north-western and south-western counties of England with scattered colonies elsewhere. It is absent from the Outer Hebrides, Orkney, Shetland, Ireland, the Isle of Man and the Channel Islands. The adult insect first emerges in south-west England, where it may be seen from the beginning of May. It emerges in the second half of May in other parts of England and generally does not make an appearance in Scotland until early June. The early emergence of the species in south-west England often gives rise to a partial second brood, which appears there in August.

I can’t wait to get back and have several more trips planned this year …

References:

Saturday, 2 June 2018

Return of selene …

Small Pearl-bordered Fritillary (Boloria selene)




Apart from the unbearable temperature, the one thing I will always remember from the summer of 1976, was the abundance of the Pearl-bordered Fritillary Boloria euphrosyne and Small Pearl-bordered Fritillary B. selene. They appeared that numerous in my local woodlands that we took them for granted; after all they would always be there - or so we thought - and of course we were wrong. The last Small Pearl-bordered Fritillary of Sussex descent ever to fly in the county was seen on Saturday, 29th June 2013. At some point during the first week of July that year the species went extinct, both locally and regionally within Sussex.

The habitat requirements of selene and euphrosyne have historically demonstrated a degree of overlap and, on many sites, the two species used to fly together and they certainly did this in my old local hunting ground amongst the forestry plantations of Worth Forest in West Sussex. However, climate change has probably reduced this overlap and, more importantly, has most likely been one of the main driving forces behind the decline and regional extinction of selene.

Now the subject of a reintroduction programme, Butterfly Conservation’s Fritillaries for the Future project, it has recently, following intensive research by project leader Neil Hulme, been reintroduced to its former final outpost. Sunday, 11th June 2017 saw the successful completion of the first part of the programme when more than 400 selene were released as either final instar larvae or adults to Butterfly Conservation’s Park Corner Heath and Rowland Wood reserves and the Forestry Commission’s Abbot’s Wood. Early signs are encouraging with the habitat looking superb during my recent visits to Park Corner Heath and Rowland Wood. I look forward to returning soon. The above images (top to bottom) show (i) male underside, (ii) male upperside, and (iii), female upperside.

References:

Blencowe, M. and Hulme, N. (2017). The Butterflies of Sussex. Newbury, Berkshire: Pisces Publications on behalf of Butterfly Conservation (Sussex Branch), pp. 146-151.

Sunday, 27 May 2018

Decline and deceit …

Lapwing (Vanellus vanellus)


Also known as the Peewit in imitation of its display calls, its more familiar vernacular name describes its wavering flight. Its black and white appearance and somewhat round-winged shape in flight make it distinctive; even without seeing its splendid crest and beautiful dark green, purple and copper plumage. This once familiar farmland bird has suffered significant declines and is now a Red List species - with changes in farming practices being the main recent cause of this decline. Targeted conservation work on individual farms in my home county of Sussex have brought notable increases in breeding pairs, but there are not enough of these intensive schemes to make a difference at a landscape and population scale. Success on many nature reserves is at best patchy and any recovery, if it happens, looks likely to be slow.

The above image was taken in the Outer Hebrides in May 2017.

References:

Barfield, C., 2014. Lapwing. The Birds of Sussex. Thetford: British Trust for Ornithology (BTO) Books on behalf of the Sussex Ornithological Society, pp. 243-245.
Pepper, R.T., 1996. Lapwing. Birds of Sussex. Sussex Ornithological Society, pp. 244-246.

Monday, 14 May 2018

Genetic engineering ...

Wood White (Leptidea sinapis)

A pair of L. sinapis (male above) exhibiting courtship behaviour.


Uncovering cryptic biodiversity is essential for understanding evolutionary processes and patterns of ecosystem functioning, as well as for nature conservation. European butterflies are arguably the best-studied group of invertebrates in the world. The discovery, some twenty years ago, of a cryptic species within the Wood White, L. sinapis, was a significant event and, since then, these butterflies have become a model to study speciation. Cryptic species are not separable based on their external morphology but can often be distinguished by dissection of the male and / or female genitalia. In addition, genetic data also supports species level separation.

In the 1940s Williams investigated the identity of the Irish Wood White L. sinapis. From looking at subtle differences between voucher specimens, he came to the conclusion that Irish examples were distinct from those found on mainland Britain and, as such, proposed that the Irish butterfly should be given the status of subspecies, which he named juvernica.

Across Europe, seven species of Leptidea have now been described: sinapisrealijuvernicaduponcheliamurensismorsei and lactea. The last three are essentially Asian species but duponcheli, a butterfly of Eastern Europe and Asia Minor, is found very locally as far west as the South of France. L. sinapis appears quite widespread on the continent as well as occurring in both Britain and Ireland. In the 1970s and 1980s Réali, and later Lorković, undertook research involving dissections of sinapis. They concluded that sinapis was not a single species but was really two cryptic species. Both species looked identical to the naked eye, did not interbreed and only upon dissection of their genitalia were they found to be separable. The new species was named Leptidea reali, Réal’s Wood White.

More recent investigations of museum specimens by Spanish and Russian lepidopterists (Dincă and colleagues) have thrown further light on the identity and distributions of the Wood Whites across Europe, using techniques based on chromosome counts and DNA analysis. Their conclusions are that reali is not in fact a single species but is itself made up of two distinct species - now named reali and juvernica. They are separate entities from sinapis. Therefore, with the benefit of access to museum specimens, what was previously thought to be a single species of Wood White is, in fact, three species - sinapis, reali and juvernica. The Cryptic Wood White, juvernica, is found across Ireland with the exception of the Burren. Current evidence suggests that there is no overlap in distribution between sinapis and juvernica; sinapis being confined to areas of the Burren limestone district in Clare and southeast Galway in the west of Ireland.

More at:

Dincă, V., Lukhtanov, V.A., Talavera, G. and Vila, R. (2011). Unexpected layers of cryptic diversity in wood white Leptidea butterflies. Nature Communications, 2, p. 324, DOI: 10.1038/ncomms1329.
Sachanowicz, K., Wower, A. and Buszko, J. (2011). Past and present distribution of the cryptic species Leptidea sinapis and L. reali (Lepidoptera: Pieridae) in Poland and its implications for the conservation of these butterflies. European Journal of Entomology, 108, pp. 235-242.