About Thymelicus acteon (von Rottemburg, 1775)
Scientific name: Thymelicus acteon (von Rottemburg, 1775)
Description Male Lulworth skippers have a wingspan of 24 to 27 millimetres (0.94 to 1.06 in), while females have a wingspan of 25 to 28 mm. This makes the Lulworth skipper one of the smallest butterflies in Britain, and the smallest member of the Thymelicus genus across Europe. Among Britain's five "golden" skippers (the others are the silver-spotted skipper Hesperia comma, large skipper Ochlodes sylvanus, small skipper Thymelicus sylvestris and Essex skipper Thymelicus lineola), the Lulworth skipper is both the smallest and darkest. Beyond its small size, it is most easily distinguished by its dark, dun-coloured wings that have olive-brown tinges, and this darkening is especially prominent in males.
Color variation is known across the species' range. In north-west Africa, the uppersides of the forewing and hindwing are darker, with subtle greenish or greyish brown tones. Similarly colored races are also found in Spain, Elba, Crete, and other eastern Mediterranean islands. The endemic Canary Islands subspecies T. acteon christi shows distinct color variation, with defined yellow-orange markings on the uppersides of its forewings.
This butterfly is sexually dimorphic. Females have a distinct circle of golden marks on each forewing, often called "sun-ray" markings because they resemble the rays around the eye of a peacock's feather. Males may sometimes have these markings, but they are noticeably fainter.
Distribution and habitat The Lulworth skipper occurs locally across southern and central Europe, Asia Minor and North Africa, where its overall population is considered stable. In northern Europe, its numbers and range have declined severely, most drastically in the Netherlands where it is now extinct. This decline has led to the species being classified as vulnerable across Europe. Isolated populations in Armenia are also threatened, though the species has not yet been added to Armenia's National Red List. It is also listed as threatened under the United Kingdom Biodiversity Action Plan.
In Great Britain, where the species reaches the northern limit of its range, its distribution is restricted to the southern coastline of Dorset. Here, both its total population and range have changed very little in recent decades, and it is locally abundant. The majority of its colonies are found on the coast between Weymouth and Swanage, and on the Purbeck Ridge, an inland line of chalk hills. Two additional outlying colonies exist at Burton Bradstock and on the Isle of Portland; the origin of the Portland colony is unknown, but it is thought to stem from either natural colonisation or released specimens. There is evidence that the Lulworth skipper is now more abundant in Dorset than at any other point since it was first discovered there in 1832. While colonies once existed in Devon, the species has not been recorded in the county outside of single sightings since the 1930s. Occurrence records exist for Cornwall, but none have been verified as representing native colonies.
Lulworth skipper habitats are primarily unfertilised calcareous grassland; in Britain this includes chalk downland, coastal grassland and undercliffs. Tor-grass, the butterfly's sole food plant and the plant on which it lays eggs, is widespread across all these habitats. The species favours tall, ungrazed grass for oviposition and larval development. It has benefited from the move away from intensive sheep grazing over the last century, as well as from recent myxomatosis outbreaks among rabbit populations that would otherwise keep grass heights low. However, evidence suggests that light, minimal grazing is not harmful to the species, and may actually be beneficial by encouraging the growth of nectar-producing flowers that adult butterflies feed on.
Life cycle Females lay their eggs in rows of 5 to 6, though clutches as large as 15 have been recorded, on the flower sheath of Tor-grass (Brachypodium pinnatum). They prefer the dead sheaths of tall plants. The care females take when selecting an egg-laying site is considered the only unusual part of the Lulworth skipper's breeding process; the rest of the process is typical for skipper butterflies. After hatching, the 2.5 cm (1 in) long larva spins a compact cocoon directly at the eggshell site, where it overwinters until around the third week of April. It then eats its way out by creating a small hole in the side of the grass sheath. The caterpillar then moves to find tender Tor-grass blades, and feeds by chewing notches into the blade margins. During the larval stage, each caterpillar lives alone inside a tube made by binding the two edges of a grass blade together with silk. The caterpillar spins a new larger tube as it grows. Lulworth skipper caterpillars reside in the warmest part of a grass clump, at a height of 20 to 40 centimetres (8 to 16 in).
The pupal stage lasts for around two weeks, beginning at the start of June and continuing until late July. The pupa forms inside a loose "nest" of silk and grass, spun deep within a Tor-grass tussock. Adult butterflies (imago) begin emerging in early mid-July and finish emerging by mid-September. Adults typically live for five to ten days, which is the normal lifespan for a non-hibernating butterfly in this seasonal stage. Adults only fly during strong sunshine and tend to form distinct discrete colonies; the largest colonies can hold up to 100,000 individuals.
