Sunday, October 04, 2015

Brown Hairstreak / Guldhale

Thecla betulae

The Brown Hairstreak has a wing span of 33-41 mm. It is easy to recognize by the golden colours of the underside and the marked black/white lines. From the upperside the female is recognizable by the large, orange spot on the front wing. The male can - seen from the upperside - look like the Satyrum-species, but these always keep their wings folded during rest.

The flying period is from first August til mid September and sometimes even later. The flying period starts later than any other Danish butterfly. Brown Hairstreak lives in pastures and light-open thickets and glades with a large growth of blackthorn or cherry plum. It overwinters as egg upon the branches of the fodderplant, and the caterpillar first develops inside the egg in spring. The caterpillar's fodderplant are blackthorn (Prunus spinosus), cherry plum (P. ceracifera) and sometimes plum (P. domestica), wild cherry (P. avium) or other Prunus-species.

The flight of this butterfly is fast and restless, but the species spend much time in the treetops, where they sit in the sun with half spread wings or seek food like honey dew. They also seek to thistle, yarrow, goldenrod, hemp-agrimony, heather or other flowers or to overripe fruit (i.e. fermenting blackberry still on the vines). Females, who need much energy by the oviposition, are seen more often on flowers and fruit than males.

Brown Hairstreak is in some years seen in large numbers, but as a rule it is few in number and difficult to find. It is in decline in the agricultural areas. It is very susceptible to pesticides and is never seen in sprayed areas. It has disappeared from some places on the Danish islands during the 1950s.

Source: Michael Stoltze, Dagsommerfugle i Danmark, 1997.

Black Hairstreak/Slåensommerfugl , Satyrum pruni,  - is a very rare butterfly, today seen in Midwest- England. It might be extinct in Denmark. Not seen since 1987.

White-letter Hairstreak/ Det hvide W/ Satyrum w-album, ccommon in most of Denmark but might be diminish because of the sick elm-trees.  

The Ilex Hairstreak /  Egesommerfugl / Satyrum ilicis, is  close to extinction  in Denmark, only known from one place.

The Purple Hairstreak/ Blåhale  (Neozephyrus quercus) common in Denmark

text and photo: grethe bachmann
photo of Brown Hairstreak, Sletterhage, Helgenæs August 2007: grethe bachmann

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