Pl. 97.
Green Hairstreak. Eggs, natural size and enlarged; caterpillar and chrysalis.
The Black Hairstreak (Thecla pruni).
This butterfly is figured on Plate [96.] In colour it is dark brown or, when quite fresh, brownish-black; there are some orange marks on the outer margin of the hind wings, and these are most distinct in the female, in which sex there are orange spots on the fore wings also. The male has a pale sexual mark at the end of the cell of the fore wings, but this is less distinct than in the following species. The under side is brown, with a bluish-white interrupted transverse line on each wing, that on the hind wings angled before reaching the inner margin. All the wings have an orange band on the outer margin, but on the fore wings of the male this is often indistinct; there are some white-edged black spots before it, and, on the hind wings, beyond it also.
The eggs are laid in July on the twigs of blackthorn, but the caterpillars do not hatch until the following spring. The egg figured on Plate [97] was reddish-brown and appeared rather shiny. The caterpillar is described as yellowish-green, with a darker green furrow and purplish ridges along the back; the latter are edged with whitish and the divisions between the rings are yellowish. The head is pale brown. The chrysalis, which is attached by the tail and has a silken thread around it, is black, marked on the head and body with yellowish-white.
The caterpillars feed on blackthorn (Prunus spinosa) in a state of nature, but will eat the leaves of damson in confinement. They may be obtained in May, in their particular haunts, by beating sloe bushes with a beating tray, or an inverted open umbrella, held under to intercept the evicted caterpillars, etc.
This butterfly was not known as British until 1828, when a number of specimens were captured at Monkswood in Huntingdonshire. These were sold by the captor as T. w-album, which was then called the Black Hairstreak. As soon as the mistake was detected, it was given out that the specimens had been taken in Yorkshire, but this was only a ruse, as T. pruni has never occurred in that county. It is confined, so far as Britain is concerned, to three or four of the midland counties. "Mr. Herbert Goss, who has found it at Barnwell Wold, and in other wooded districts of Northamptonshire, at intervals, for more than twenty years past, says that it is fond of sitting on the flowers of privet (Ligustrum), and of Viburnum lantana, in the woods, and sometimes is to be found in numbers. Its time of emergence is very variable, apparently regulated by the lateness of the spring—from June 17th to the first week in July. Reared specimens made their appearance from June 13th to 27th. He writes, 'It was the greatest possible pleasure to see them walking about the table while I was at breakfast.' In 1858 it was found commonly at Kettering, and in 1859 at Oundle, and has been recorded at Warboys Wood, Huntingdonshire, and in Buckinghamshire. One specimen was taken at Brandeston, Suffolk, by the Rev. Joseph Green; and Mr. Allis found it commonly in the Overton Woods and about St. Ives. There is also a record in Monmouthshire, which may require confirmation. This butterfly does not appear to be losing ground in this country, its fondness for trees and lofty bushes rendering it difficult to capture" (Barrett).