Otter Moth
(Hepialus Humuli). This insect, which is, perhaps, more widely known by the names "Ghost Moth" and "Ghost Swift," belongs to a well-characterised group of Moths, included under the genus Hepialus, which are popularly known as "Swifts," because of the rapid darting flight of most of the species. Five species are native in Britain, the Ghost Swift being the largest and most conspicuous, because of the white upper surface of the wings of the male, and its peculiar hovering flight in the dusk of evening. The attraction to the frequented spot is probably a female, concealed among the herbage, above which the male swings almost with the sweep of a pendulum. The popular name of "Ghost" is due to the colour, and to the sudden disappearance of the insect when it settles down among the herbage. The Swifts are readily recognised by their antennae being slender and very short, not reaching to the back of the thorax; and, in addition, the wings are long and rather narrow, with a space between the front and hind pairs, on each side, just at the roots. They all fly in the evening twilight. The larvae are long, and rather slender; and in colour are greyish or dull yellow, with a brown head, and a brown, horny plate on the back of the second ring of the body. They feed on the roots of many herbaceous plants, burrowing into those large enough to allow of their entrance. They change, in cocoons spun in the larger, or amongst the smaller, roots, into brown pupae, with long bodies, strongly ringed, each ring bearing short stiff hairs, by means of which the pupae push their way to the surface of the soil before the moths emerge from them.
The male Otter Moth, in the usual form, as stated above, has all the upper surface of the wings silvery-white, with brown fringes; but, in the Shetland Islands, varieties occur that show all transitions in colour between the ordinary male and the female. The female reaches about 2 1/2in. or 2 3/4in. in spread of wings, while the male averages only about 2in. The front wings of the female are yellow in colour, with irregular spots, and a broken band near the hind margin, brick-red; the hind wings are dull leaden-grey at the base, tawny near the margin. The larvae of the Otter Moth, and probably of the common Swift also, sometimes eat roots of Hops, and of a few garden plants, but, fortunately, seldom prove very injurious. The only sign of their presence is the withering of the plants without visible cause. Remedies. The roots should be examined, and the larvae of every kind in or upon them should be destroyed. Probably, solutions of paraffin, of carbolic acid, or of other insecticides, would be found beneficial, if the plants were watered with them.