Sunday, 20 July 2014

io ...

Peacock (Aglais io)

The Peacock (A. io) must arguably be one of Britain’s most attractive butterflies, if not the most.

A familiar sight in gardens across the British Isles, it is unmistakable, with quite spectacular markings on the upperside of the wings that give this stunning butterfly its name. The underside is a different matter altogether, being almost entirely black, providing perfect camouflage when the butterfly is at rest or during hibernation. In addition to camouflage and large eye-spots, the butterfly is able to make a hissing sound by rubbing its wings together - this can be audible to human ears. This is a highly mobile species that occurs throughout the British Isles, including Orkney and Shetland, although it is not found in some parts of northern Scotland.

Undoubtedly one of my favourites …

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Sunday, 13 July 2014

Hair today, gone tomorrow …

White-letter Hairstreak (Satyrium w-album)

I have recently been checking nearby localities for the presence of native elm (Ulmus spp.). Unless you live in Brighton of course, where the national collection is housed, elm has nowadays become a somewhat rare component of the British countryside, mainly due to the devastating effects of Dutch elm disease (DED) - one of the most serious arboricultural diseases in the world. Our main native species, English elm (Ulmus procera), smooth-leaved or field elm (U. minor) and Wych elm (U. glabra) are all susceptible to Ophiostoma novo-ulmi, a highly aggressive pathogen of the disease first noted in Britain in the late 1960s. It is disseminated by various species of elm bark beetles. Within a decade of its arrival about 20 million elms out of an estimated UK population of 30 million were dead. By the 1990s this number was probably well over 25 million. The disease still persists in the UK. The less virulent Ophiostoma ulmi first reached the UK in 1927.

Elm is unfortunately the sole foodplant of S. w-album and this species has undoubtedly suffered as a result of DED, especially in its southern distribution. As all species of elm are affected there was concern that this species might become extinct in the British Isles as a result. Surviving colonies were subsequently looked for in order to obtain a better understanding of the distribution of this species. Several new colonies were discovered which gave hope for the future of this vulnerable butterfly. In addition, there has been a concerted effort to find disease-resistant elms that exhibit the appropriate qualities to support this butterfly (such as flowering at the right time of year - since young larvae generally rely on flower buds as a food source).

S. w-album is never found far from its larval foodplant, U. glabra being the preferred choice. Flowering elms are usually essential for successful larval development and this therefore suggests a certain maturity of tree, although there is some evidence that this species has successfully used non-flowering elms on occasion. Favoured sites are elms on the edge of deciduous woodland, but this species can also be found in more open habitat including roadside verges, such as the individual female figured above, if suitable elms are present.

The butterfly forms discrete colonies, which are sometimes very small containing only a few dozen individuals. These are typically focused on a small clump of trees or even an individual tree. They are not great wanderers and will reuse the same locality year after year. This elusive species is found throughout England, south of a line stretching between South Lancashire in the west and South Northumberland in the east. It is found more locally in Wales, and is not found in Scotland, Ireland or the Isle of Man.

Check out the elms near you …

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Sunday, 6 July 2014

Femme fatale …

Purple Emperor (Apatura iris)

The Purple Emperor (A. iris) is a magnificent and elusive insect that is actively sought out by the many subjects of ‘His Majesty’, as the male butterfly is affectionately known. A. iris spends most of its time in the woodland canopy where it feeds on aphid honeydew, with the occasional close encounter when it comes down to feed on sap runs or, in the case of the male, animal droppings, carrion or moist ground that provide much-needed salts and minerals. Those that make annual 'pilgrimages of obsession' to see this spectacular creature will often try and lure the males down from the canopy using all manner of temptations - including shrimp paste, banana skins and human urine.

The male butterfly, which typically emerges in early July, sometimes at the end of June in good years, is undoubtedly one of the most beautiful and sought after of all of the butterflies found in the British Isles. From certain angles it appears to have black wings intersected with white bands. However, when the wings are at a certain angle to the sun, the most beautiful purple sheen is displayed, a result of light being refracted from the structures of the wing scales.

The female, on the other hand, is a deep brown and does not possess the purple sheen found in the male. She is also a much rarer beast and an audience with an Empress is one to be cherished …

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Thursday, 3 July 2014

Distant memories ...

Large Tortoiseshell (Nymphalis polychloros)

Although I have seen polychloros on the continent, including its larval webs, many seasons have passed since I have seen this beautiful butterfly in Britain - and then only a single specimen.

In Victorian times N. polychloros was considered widespread and common in woodland in southern England. However, this stunning insect has subsequently suffered a severe decline to a point of extreme scarcity. N. polychloros, whose numbers were always known to fluctuate, is generally believed to be extinct in the British Isles, with any sightings considered to be migrants from the continent or accidental or deliberate releases of captive-bred stock. Several causes of its decline have been suggested - including climate change, parasitism, and the effects of Dutch elm disease on one of its primary larval foodplants, Ulmus spp. The hope, of course, is that this butterfly is able to once again colonise our islands, and some hope revolves around the few limited sightings from the Isle of Wight each season. Although previously found in many parts of England, Wales and Scotland, the greatest concentrations were in the midlands, south and east of England. This species has not been recorded from Ireland. Recent sightings have come from the south coast, in particular from South Devon, South Hampshire, the Isle of Wight and West Sussex.

I won't hold my breath but fingers crossed …

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