HEPIALIDAE
Five species of this family are found in the British Isles, all of which have been recorded in Dorset. They are medium to large, wingspan 25 to 50 mm, and most exhibit a strong crepuscular flight when many hundreds of individuals of a given species may be seen on occasion, oscillating from side to side a foot or so above the ground. Thereafter they fly small distances through the night; moreover, in the author’s experience, those attracted to light traps represent a small proportion of the colony size. The unglamorous maggot-like larvae develop beneath the ground feeding on the roots of a variety of plants, with bracken or grass roots sought by the majority. Well-marked imagines of all species are relatively straightforward to identify; more care is required with less well-marked examples. The most often to be confused are Common Swift and Orange Swift, although these two species tend to fly at different times of the year.
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14 Hepialus humuli (Linnaeus, 1758) GHOST A widespread species in the British Isles, the larva feeding on the roots of grasses and other plants that include nettle (Urtica spp.), burdock (Arctium spp.), dandelion (Taraxacum spp.) and dock (Rumex spp.). In Dorset, the moth ranges from common on some unimproved alkaline grasslands, to local on sandy soils further east; it is virtually absent from heathland. The species “has not constituted an agricultural pest, but prior to the widespread use of pesticides in agriculture occasionally proved troublesome in flower gardens” (per W Parkinson Curtis manuscript).
15 Hepialus sylvina (Linnaeus, 1761) ORANGE SWIFT A species occurring in most parts of the British Isles, the larva feeding for two years on the roots of bracken (Pteridium aquilinum), dandelion (Taraxacum spp.) and dock (Rumex spp.). In Dorset, the moth is abundant on unimproved grassland and in woodland harbouring bracken. A number of adults trapped in urban and ruralareas where bracken, dandelion and dock plants are not dominant (for example calcareous grassland), suggests that larvae flourish on roots of other plants; the following record supports this: St Albans Head, larva found in viper’s bugloss (Echium vulgare) root, adult emerged on 6 September 1938 (H Andrewes).
16 Hepialus hecta (Linnaeus, 1758) GOLD SWIFT A local species in the British Isles, the larva feeding for two years on the roots of bracken (Pteridium aquilinum). The adult male is said to exude a scent reminiscent of pineapple. In Dorset, the moth is rather local, preferring the shelter of woodland on acid and clay soils where bracken abounds. The oscillating dusk flight of this species has been observed by the author immediately above bracken canopy in Chase Woods, in Holt Wood and close to Hardy’s monument on the summit of Black Down in June and early July.
17 Hepialus lupulinus (Linnaeus, 1758) COMMON SWIFT A species with a wide distribution in the British Isles, the larva feeding on the roots of various wild and cultivated species of grasses and plants. In Dorset, the moth is abundant on unimproved grassland, rare on heathland, and moderately common elsewhere. The moth formerly, “on occasions, rose to the position of a minor agricultural pest on tuberous rooted plants with corms of the Gladiolus type” (per W Parkinson Curtis manuscript).
18 Hepialus fusconebulosa (DeGeer, 1778) MAP-WINGED SWIFT A local species in the British Isles, the larva feeding for two years on the roots of bracken (Pteridium aquilinum). The moth has been recorded from areas of bracken within a single locality in Dorset, Batcombe Down, where it was first discovered by J Astley in 1998. The habitat is unimproved chalk grassland. Further colonies may be discovered on leached chalky soil summits where bracken occurs. This ‘Swift’ is on the wing at the same time as the Common Swift.
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