BUTTERFLIES AND MOTHS. 335 



the Basses Alpes. We have thus in the Maritime 

 Alps three out of the four European Swallow-tails ; 

 the fourth, P. Hospiton, is confined to Corsica. 



The distribution of a butterfly is governed by that 

 of its food plant, and this depends in great measure 

 on the nature of the soil. Elevation is a less impor- 

 tant factor. Satyrus Arethusti does not reach the 

 elevation of 3,000 feet in the Vesubia Valley, but it is 

 plentiful at Caussols, above Grasse, at 3,800 feet. The 

 Painted Lady (V. Cardui), whose larva eats the 

 thistle, is universal, like that weed, and seems to care 

 nothing about elevation. You may see it battling, 

 with ragged wings, against the mountain breeze, 

 8,000 feet above sea-level. Other Butterflies appear, 

 like that page in Marmion, unable to brook the chilly 

 air ; but the fact is that they are tied to their food 

 plant, which grows upon the sheltered coast. The 

 Apollo, depending on Saxifrage and Sedum, does not 

 descend much below 3,000 feet. 



Thus a knowledge of Botany is the key to the 

 study of the Lepidoptera. More numerous and more 

 perfect specimens are obtained by searching for the 

 larvre on their proper food plant than by racing about 

 in the burning sun. You may collect caterpillars 

 towards evening, when the heat has abated and the 

 valley is in shade. These larvae are brought up in 

 cages, carefully protected against ichneumons. When 

 they have pupated, they are transferred to a ventilated 

 case designed for the purpose. 



The greatest drawback to Butterfly collecting is 

 that, even when kept in expensive cabinets, the 

 insects are rapidly destroyed by breakage, " grease," 

 and mites. Unless constantly renewed bv fresh 



