The ghost moth or ghost swift (Hepialus humuli) is a moth of the family Hepialidae. It is common throughout Europe, except for the far south-east.

Female ghost moths are larger than males, and exhibit sexual dimorphism with their differences in size and wing color. The adults fly from June to August and are attracted to light. The species overwinters as a larva. The larva is whitish and maggot-like and feeds underground on the roots of a variety of wild and cultivated plants (see list below). The species can be an economically significant pest in forest nurseries. During the lekking period, incident light intensities between 10.0 and 2.0 lux have been found to increase the brightness contrast between the background (grass/plants) and male moths' silver/white wings. It is thus believed that the male wing color may have evolved as a secondary adaptation to aid in the moth's visibility.

Displaying

The male ghost swifts display by hovering directly above vegetation, while occasionally shifting slowly horizontally. The displaying male only occasionally made vertical movements to shift display positions. Females are attracted to the displaying males in leks, and once a female chooses a male, she will pass within a few centimeters of him. The male will follow the female, who will land and beat her wings, signaling that the male may approach her. The two moths will then copulate. While aggregating in leks, male ghost swifts use pheromones.. These are emitted in order to attract a female, but they are not known to be used as an aphrodisiac. The main component of the male pheromone (in the distantly related species Phymatopus hecta) is (E,E)-α-Farnesene.

The olfactory substances used to attract females are produced on the male's hind tibial brushes, and were said to be "goat-like", meaning the smell of the Goat Moth caterpillar. Males may also be attracted to stationary females by olfactory stimuli.

Sexual dimorphism

thumb|Female ghost moth (left) and male ghost moth (right)

The ghost moth displays high levels of sexual dichromatism (see picture right). Female ghost moths are a yellow-brownish color, while males have silver/white wings. It has been suggested that the difference in wing color between males and females is used for visual epidemic signaling. The females lack the intricate morphology of the males. The underside of both the male and female ghost moth is a uniform grey/brown color.

thumb|140px|left|Figs. 3. 3a, 3b larvae after last moult 3c pupa

Larva

The ghost moth larvae grow up to 50 mm long and have a white opaque body with a red/brown head.

Subspecies

  • Hepialus humuli humuli
  • Hepialus humuli thulensis <small>Newman, 1865</small> (Great Britain, Faroe Islands)

Ghost moth in folklore

It is believed that the common name of "ghost moth" for Hepialus humuli may have originated from European folklore, as there are numerous references to white moths being the souls of the departed.

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File:Faroe stamp 245 Hepialus humuli.jpg|Ghost moth on a Faroese stamp

File:Hepialus humuli f.jpg|Female

File:Hepialus humuli m.jpg|Male

File:Hepialus humuli, Ghost Moth, Trawscoed, North Wales, Nov 2013 (21418448681).jpg|Larva

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References

  • Chinery, Michael (1986, reprinted 1991). Collins Guide to the Insects of Britain and Western Europe.
  • Skinner, Bernard (1984). The Colour Identification Guide to Moths of the British Isles.
  • Lepiforum e.V.