THE SWALLOW-TAIL AND THE 'WHITES' 141 



insect is first seen in May, and is more or less abundant from this 

 time to the month of August. 



Family PIE RID ^E 



This family, though known commonly as the ' Whites,' contains 

 four British species that display beautiful tints of bright yellow or 

 orange. 



In many respects the Pieridce resemble the last species. Thus 

 the perfect insects have six fully developed legs ; the caterpillars 

 are devoid of bristles or spines ; and the chrysalides are attached 

 by means of silky webs at the ' tails,' and strong cords of the same 

 material round the middle. 



All the larvae are also cylindrical or wornilike in shape ; and 

 their skins are either quite smooth, or are covered with very short 

 and fine hairs, that sometimes impart a soft, velvety appearance. 



The members of this family are remarkable for their partiality 

 for certain of our cultivated plants and trees ; and are, in some 

 cases, so abundant and so voracious, that they are exceedingly 

 destructive to certain crops. 



The Black -veined White (Aporia Cratcegi) 



This butterfly may now be regarded as one of our rarities. At 

 one time it was rather abundant in certain localities in England, 

 among which may be mentioned the neighbourhoods of Cardiff and 

 Stroud, also parts of Kent, Sussex, Hampshire, Huntingdonshire, and 

 the Isle of Thanet ; but it is to be feared that this species i& nearly 

 or quite extinct in this country. It is well, however, not to give up 

 the search for it, and if you happen to be in one of its favoured 

 localities of former days, you might net all the doubtful ' Whites ' 

 of large size that arouse your suspicions, liberating them again if, 

 on inspection, they do not answer to the description of the species 

 ' wanted.' This course becomes absolutely necessary, since the 

 Black- veined White is hardly to be distinguished from the Common 

 Large White while on the wing. 



If you examine a number of British butterflies you will observe 

 that in nearly all species the wings are bordered by a fringe of hair, 

 more or less distinct. But the case is different with Cratcegi. Here 

 they are bordered by a black nervure, without any trace of fringe, 

 thus giving an amount of rigidity to the edges (see Plate I, fig. 2). 



The wing rays, or nervures, are very distinct a feature that 



