This is very much like the last in appearance, and has often been mistaken for it by inexperienced eyes. The points of difference are—on the upper side, the absence of the orange band at the hinder edge of the hind wings, and the presence of a bluish grey circumflex line at the inner angle; here also is sometimes a small orange dot;—beneath, the orange band forms a series of arches, bounded on the edge nearest the root of the wing by a clear black line instead of the rounded black spots seen at this part in Pruni.
The caterpillar, which feeds on the elm, is wood-louse shaped; pea-green, barred with yellow; head black. May be beaten off elm trees in May.
The butterfly appears in July, and is found in various situations, sometimes flying high up round elm trees, sometimes descending to bramble hedges, or fluttering
about in weedy fields a foot or two from the ground. It was formerly a much rarer insect than at present, and now its appearance in any given locality is a matter of much uncertainty. Mr. J. F. Stephens writes as follows to the Zoologist:—
"For eighteen years I possessed four bleached specimens only of Thecla W. Album, having vainly endeavoured to procure others, when, in 1827, as elsewhere recorded, I saw the insect at Ripley, not by dozens only, but by scores of thousands! and although I frequented the same locality for thirteen years subsequently, sometimes in the season for a month together, I have not since seen a single specimen there; but in 1833 I caught one specimen at Madingley Wood, near Cambridge."
Other localities:—Near Sheffield; Roche Abbey; York; Peterborough; near Doncaster; Polebrook, Northants; Allesley, Warwickshire; Brington, Huntingdonshire; Yaxley and Monks Wood, Cambridgeshire; Needwood Forest, Staffordshire; Wolverston, near Ipswich; Chatham; Southgate, Middlesex; West Wickham Wood; Epping; Bristol.
THE PURPLE HAIR-STREAK.(Thecla Quercus.)
([Plate XII]. fig. 4, Male; 4 a, Female.)