The Short-tailed or Bloxworth Blue (Cupido Argiades)
The interesting little butterfly represented on Plate 103 was not known to occur in Britain until 1885, when the Rev. O. Pickard Cambridge made the startling announcement that his sons had captured two specimens, a female on August 18th, and a male on August 20th of that year, the scene of capture being Bloxworth Heath, Dorset. Shortly after this fact was made public the Rev. J.S. St. John added a record of two males that he had discovered in a small collection of Lepidoptera made by Dr. Marsh, who stated that he had taken the specimens of C. argiades in 1874, close to a small quarry near Frome. In addition to these a specimen, also recorded by Mr. Cambridge, was taken at Bournemouth in August, 1885; one is reported to have been captured at Blackpool, about 1860; and one at Wrington, about twelve miles north of Bristol, in 1895 or 1896.
The following details of the early stages are obtained from Mr. Frohawk’s life-history of the species published in the Entomologist for October, 1904. The egg (Plate 102, figured from a photomicrograph by Mr. Tonge) is of a pale greenish-blue, but varies both in the extent of the ground colour and in the structure of the reticulations, which are white, resembling frosted glass.
The full-grown caterpillar (August 23rd) measures 3/8 inch in length. It is of the usual wood-louse shape, with only a very shallow furrow on the back, bordered on each side by a fringe of spinous bristles, which vary in length; the whole surface is densely studded with shorter but similarly formed whitish or brownish bristles. The ground colour is pale green, with a darker green stripe along the centre of the back, and fainter green oblique stripes on the sides. The head is black and shining, and is hidden under the first ring when the caterpillar is not feeding or moving about.
The caterpillars hatched on July 30th, from eggs that were laid in the South of France on July 24th, and were reared on bird’s-foot trefoil (Lotus corniculatus), of which they ate the flowers, seeds, and leaves.
The chrysalis, which is attached to the food-plant by a silk pad at the tail and a thread round the body, is pale green and very finely reticulated; the wing-cases are rather whiter green, sprinkled with minute black specks, and the veins are white; there is a blackish line along the centre of the back, but this is only well defined on the head and thorax. The whole surface, except the wings, is sprinkled with slightly curved and moderately long white hairs.
The butterfly emerges in about ten to fourteen days, according to temperature.
The male is violet-blue with the veins rather darker; the outer margin is narrowly bordered with blackish, and there are some black dots on the outer margin of the hind wings; the fringes are white, and there is a slender tail on the hind wings. The female is brownish, tinged with violet towards the base; the hind wings have black spots on the outer margin, and some of these are inwardly edged with orange; the tails are slightly longer than those of the male.
All the available information concerning the occurrence of this species in England has already been given. No doubt the localities from which specimens were recorded have been closely investigated during the past twenty years, but no further captures of this butterfly have been recorded. This seems to indicate that it is not really indigenous, but that its presence here may possibly have been due to accidental introduction.
The spring form, polysperchon, is smaller than the specimens occurring in the summer, but so far that form has not been seen in England.
The species is widely distributed over Central and Southern Europe, and its range extends through Northern Asia to Amurland, Corea, and Japan. It is also represented in Northern and Central America by var. comyntas, and has been recorded from Australia.