Wood White (Leptidea sinapis)
The Wood White (Leptidea sinapis) is one of our most beautiful butterflies, with undoubtedly the slowest and most delicate flights of all the British species. Along with the Small-pearl Bordered Fritillary (Boloria selene), whose population is currently at an all time low in the county, it is probably the rarest butterfly in Sussex. When at rest, the rounded tips of the forewings provide one of the main distinguishing features between this butterfly and other similar members of the Pieridae. Adults always rest with their wings closed. In flight, the male can be distinguished from the female by a black spot at the tip of the forewings that is greatly reduced in the female. L. sinapis lives in discrete colonies and was only recently separated from the morphologically identical Cryptic Wood White (Leptidea juvernica). L. sinapis is a local species and can be found in central and southern England; and also in Ireland on the limestone pavements of Clare and southeast Galway. L. sinapis is absent from Scotland, the Isle of Man and the Channel Islands.
The English colonies emerge in late April or early May and fly until the end of June. In Ireland, the emergence starts a little later, in late May, and the adults fly until the middle of July. Some locations, especially those in Surrey and Sussex, typically experience a 2nd brood, which is characteristically on the wing between mid July and August; this can often be more substantial than the 1st brood during good seasons.
As its name suggests, L. sinapis is typically found along woodland rides and their margins. However, colonies in the southwest of its range can also be found in more open areas such as disused railway cuttings and meadows. Suitable habitat is characterised as being warm, sheltered and damp, where both larval foodplants and suitable nectar sources are in abundance. Larval foodplants include various vetches and trefoils including Bird’s-foot Trefoil (Lotus corniculatus), Bitter Vetch (Lathyrus linifolius), Greater Bird’s-foot Trefoil (Lotus pedunculatus), Meadow Vetchling (Lathyrus pratensis) and Tufted Vetch (Vicia cracca). Nectar sources include a variety of woodland flowers. During periods of hot weather, males can often be found taking mineral salts from puddles and animal dung.
Its pupa, pictured above, is the most beautiful of creatures when examined in close detail. A silken girdle and the cremaster (a hook-like tip at the base of the pupa serving as an anchorage point), as shown above, attach it to the stem. Those pupae that do not give rise to a new generation in the year of their development, overwinter and emerge as the spring brood the following season.
Further information can be found at: www.ukbutterflies.co.uk/species.php?species=sinapis
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