Black-veined moth  (Siona lineata)

Adult Black-veined moths are white in colour with black veins that are more obvious on the underside of the wings. Females differ from males in that they have slightly shorter wings and thicker, shorter bodies (3). The caterpillars are grey-brown in colour with darker lines along the back and sides (3).

This species was once known from Kent, Dorset, Sussex, Essex, and Somerset, but now remains in just four sites in Kent (1). It has a wide distribution in Europe and extends as far east as Siberia (1).

This moth inhabits lowland calcareous grasslands dominated by tor-grass (Brachypodium pinnatum) where the main larval foodplant marjoram (Origanum vulgare) is present within the sward (1).

The adults are on the wing in May and June and are largely crepuscular (7). They rest in long grasses during the day from which they are easily disturbed, sometimes flying naturally on warm, dull days (8). Caterpillars hatch from the eggs laid by the adults; they are present from July to May and hibernate through the winter, emerging the following spring when they pupate (2). The adults then emerge, starting the cycle again. This type of lifecycle is known as 'single brooded' or 'univoltine', as only one generation (or 'brood') is produced in the year.

It is thought that the drastic decline of the Black-veined moth is the result of habitat burning, whether accidental or deliberate, over-grazing and lack of suitable management leading to scrub encroachment (1). The reason for the habitat management requirements of Siona lineata, and the probable cause of the contraction of its range, is the species’ requirement for transitional calcareous grassland within a specific stage of succession. The required habitat must exhibit a well-developed sward-mosaic of grass tussocks and herb growth, of sufficient length to offer protection to larvae throughout the winter. In the past, Siona lineata was doubtless able to find alternative suitable breeding habitat when an existing site became overgrown, cultivated or otherwise unsuitable. This is no longer the case, and the maintenance of suitable habitat at existing colony sites must remain the priority (7).

The Species Action Plan produced as part of the UK Biodiversity Action Plan aims to maintain all current populations and restore a further ten populations in the historic range before 2010 (1). Since 1995, an English Nature Species Recovery Programme has worked towards meeting these aims (1).

Information authenticated by Sean Clancy.