1 70 THE BOOK OF BRITISH BUTTERFLIES. 



the anal angle bearing a roundish projection, the nervure 

 next to it a long black tail, and the next one again a 

 short one ; the fringe is pale. The ground-colour of 

 the upper surface is a deep sepia-brown, and the pro- 

 jection at the anal angle bears a small orange-red spot. 

 It should be noticed that pruni has a series of orange 

 semilunar spots on the hind-wings, otherwise there is a 

 considerable resemblance between the upper surfaces of 

 the two butterflies. The ground-colour of the under- 

 surface (Fig. 187) of W-albnm is pale brown with a white 

 irregular streak across all the wings, that on the hind- 

 wings taking the form of a W. whence the specific name. 

 Outside this streak on the hind-wings is a bright red 

 band of arches bordered inwards with black, and then 

 with a slender white line. Outside the orange band is 

 a series of black spots and one blue one ; next follows a 

 slender white line, and then a black one just inside the 

 fringe. 



T. pruni, Linn. (Dark Hairstreak or Thecla of the Sloe, 

 sometimes called the Black Hairstreak) (Figs. 188 to 190), 

 is by no means a common butterfly, and was, when first 

 discovered in England, early in the present century, 

 confused with T. W-album, which it somewhat closely 

 resembles, and for which, therefore, it is still liable to 

 be mistaken. 



T. pruni is found neither in Ireland nor in Scotland, 

 and in but few counties in England and Wales, these 

 being Berks, Bucks, Hants, Derby, Huntingdon, Mon- 

 mouth, Northampton, and Suffolk. In some localities in 

 these, however, it is occasionally plentiful. 



The eggs are laid in the autumn on twigs of the 

 Sloe (Prunus spinosd)\ they hatch in the spring, the larva 

 being found in May and June, the pupa in the latter 

 month, while the imago appears in June and July. 



