THE SWALLOW-TAIL AND THE 'WHITES' 153 



among British butterflies, though we shall presently meet with 

 instances of angular projections on hind wings only. 



The ground colour of the male (Plate II, fig. 4) is a rich sul- 

 phury yellow, with a greenish tinge. That of the female is a very 

 pale greenish yellow. The only conspicuous markings are small 

 saffron spots, one near the centre of each wing. The antennae are 

 red, short, and beautifully curved ; but, unlike the two preceding 

 species, the legs are almost white. 



The eggs of this butterfly are laid in April on the two species of 

 buckthorn (Hliamnus catharticus and B. Frangula) by the females 

 that have successfully weathered the winter. They are of a bright 

 yellow colour, and are usually hatched in about a fortnight. 



The body of the caterpillar is green, and it is thickly covered 

 with little black wart-like projections. A pale stripe also runs 

 along each side. During May and June it may be found on its 

 food plants, and toward the end of the latter month it attaches itself 

 by a silken carpet and belt to the under side of one of the leaves. 



The chrysalis is of a very peculiar shape, the body being curved, 

 and the wing cases standing out prominently beyond the general 

 surface. Its colour is a bright apple green marked with yellow, 

 and it is so transparent that certain of the structures can be seen 

 through its skin. 



The perfect insect emerges in about three weeks after the change 

 to the chrysalis ; and may be looked for from July to the end of the 

 summer. This period may be regarded as the best time in which 

 to hunt for Hhamni, but it is to be noted that this butterfly makes 

 its appearance during all months of the year, even though it rs-single- 

 brooded. 



A large number seem to hybernate, and their winter sleep is so 

 light that the welcome rays of the sun on a mild day, even during 

 the bleak months of November to February, will often call them out 

 from their hiding places. Then, as a rule, the hybernating butter- 

 flies do not live long after depositing their eggs for the future 

 brood ; but the Brimstone often lives on till its offspring have them- 

 selves, attained the perfect state, so that it is possible to capture the 

 insects of two different years both on the same day. In such a case 

 it is generally easy to distinguish between the two, for the newly 

 emerged specimens are beautifully bright and fresh in colour, 

 while those of the previous year are more or less faded and worn, 

 their wings being often semi-transparent through the loss of scales, 

 and frequently disfigured by the stains of mildew. 



