The wings of the green hairstreak butterfly are dull brown on the uppersides, but bright green on the underside (1), with a white 'streak' across the fore- and hindwings (3). The sexes are very similar in appearance, but males can be distinguished by the presence of a small pale spot on each forewing (1). The plump caterpillar grows to 1.5 cm in length, and is flattened at each end. It is green in colour, with a brown head, has a dark line passing along the back and rows of diagonal yellowish-white markings (3).
One generation is produced each year (3); adults emerge from mid-April onwards (2) and the flight period is concentrated between May and early June in southern parts of England. Further north, the flight period may occur a month later (2). Females lay eggs singly on the buds or young shoots of the foodplants, after about a week the eggs hatch, and the caterpillars begin to feed (3). At the end of July the caterpillars descend to the ground, where they pupate in the leaf litter (3). The pupae produce audible squeaks, which attract ants, and a pupa has been found in a nest of the ant Myrmica sabuleti. It is believed that the pupae are buried by ants, but the species involved in this relationship are not known (2). The pupal stage hibernates, and the adults emerge the following spring (3). This species is the only hairstreak butterfly that hibernates as a pupa; it is therefore the earliest of these butterflies to emerge (2).
This butterfly has a wide distribution in Scotland and Wales. It is also found on the Inner Hebrides and Arran (2). In England it is widespread in the north on moorlands, and on calcareous grasslands of the south. It has declined in eastern areas where these habitats are absent (2). Elsewhere the species is widespread in Ireland, and occurs throughout Europe and some parts of North Africa, extending through Asia to Siberia (2).
Found in a wide range of habitats including calcareous grasslands, moorland, heathland, woodland clearings and rides, bogs, disused quarries and railway cuttings. It requires the presence of the foodplants of the caterpillars; on calcareous grasslands these are common rock rose (Helianthemum nummularium) and common bird's-foot-trefoil (Lotus corniculatus); on heathland gorse Ulex europeaus), broom (Cytisus scoparius) and dyer's greenwood (Genista tinctoria) are used, whilst bilberry (Vaccinium myrtillus) is used on moorland. A range of other foodplants is also occasionally utilised (2).
Despite being a widespread species at present, the green hairstreak has been lost in some areas as a result of habitat loss, changes in management, and neglect of sites (2). In upland areas, overgrazing is a threat, and in woodlands, over-shading has increased as a result of a decline in traditional woodland management techniques (2). Other potential threats include drainage and peat extraction in lowland areas, and tree-planting in the uplands (2).
Relatively little is known of this butterfly, and it is likely that it has been under-recorded in some areas; both research and monitoring are therefore required to gain insights into this species (2).
For more on this species see: The Millennium Atlas of Butterflies in Britain and Europe (2001). By Asher, J., et al. Published by Oxford University Press.
For more on butterflies and their conservation see the Butterfly Conservation website:
A winter survival strategy characteristic of some mammals in which an animal's metabolic rate slows down and a state of deep sleep is attained. Whilst hibernating, animals survive on stored reserves of fat that they have accumulated in summer. In insects, the correct term for hibernation is 'diapause', a temporary pause in development and growth. Any stage of the lifecycle (eggs, larvae, pupae or adults) may enter diapause, which is typically associated with winter.
Stage in an insect's development when huge changes occur, which reorganise the larval form into the adult form. In butterflies the pupa is also called a chrysalis.
The process of forming a pupa, the stage in an insect's development, when huge changes occur that reorganise the larval form into the adult form. In butterflies the pupa is also called a chrysalis.
Often the footpaths and access tracks which run through and divide blocks of trees in woodland. Many rides contain a mixture of rich flora and structure, and provide different habitat conditions for a range of wildlife.
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