64 THE BOOK OF BRITISH BUTTERFLIES. 



black spot and the hind-wings an orange one, which 

 underneath is centred with silver. The antennae are 

 red, a peculiarity which these butterflies share with the 

 genus Gonopteryx, the only species of which rhamni 

 approaches the two species of Colias in other respects 

 also. Specimens of the genus are to be found in most 

 parts of the world, many being Arctic. Some of these 

 latter, and, indeed, others of the genus, have a violet 

 or blue tinge to their wings, and so approach the Blues. 



The two British species (Figs. 52 to 58) are C. 

 hyak and C. edusa^ both of which in the larval stage 

 feed on various leguminous plants, especially two Clovers 

 (Trifolium repens and T. pratense\ Lucerne (Medicago 

 sativa), Nonsuch (M. lupulina\ &c. In each case the 

 eggs are laid in the spring, and the caterpillars are to 

 be found in June and July. They enter the chrysalis 

 state about the end of July, and are on the wing 

 from August till they retire in order to hibernate during 

 the winter. Edusa is sometimes on the wing as late as 

 November, but hyale generally retires earlier. They 

 leave their winter quarters, usually much reduced in 

 number, in May, and then the eggs are laid which pro- 

 duce the August flight. The British Edusas occasionally 

 breed in the autumn, and pass the winter in the pupal 

 (or possibly larval) stage. Indeed, it has been thought 

 of late that the winter is oftener passed in the pupal or 

 perhaps larval stage, in which case these butterflies 

 are double-brooded. 



Both species, but hyak especially, are very capricious 

 in their appearance. In some seasons edusa^ and less 

 frequently hyale^ have swarmed in many parts of the 

 south of England, the former being found also in 

 gradually decreasing numbers in the Midland counties, 

 individuals sometimes extending into the very north, and 



