XXXVII 



some of which it has never re-appeared. Years frequently occur in 

 which Edtisa, Hyale, Cardui, Antiopa, Lathonia, and Daplidicc, are 

 all, or many of them entirely absent. 



The most favourable years for the production of insect life have 

 been 1794, 1798-1800, 1808-12, 1818-26, 1830-35, 1842-44, 1855-59, 

 1868-72, and 1887. Of these 1794, 1826, 1842, and 1870 were par- 

 ticularly good years ; indeed 1826 goes by the name of the " Annus 

 Mirabilis " of British Entomologists. 



Before departing from this subject it must however be borne in 

 mind that atmospheric changes are not the sole cause of the scarcity 

 or disappearance of butterflies. The drainage of Whittlesea Mere, in 

 1851, caused the loss of Chrysophanxs dispar. An increase too of their 

 parasitic enemies among the Hymenoptera, and of the Dipterous family 

 Tabinidcz do much towards reducing their numbers. In 1853 and 1854 

 there was a plague of the caterpillars of Brassicce in Sussex. During 

 the latter season owing to the attentions of Apanteles glomeratus, the 

 number of fly-blown caterpillars was incredible, so much so that there 

 was almost a total cessation of the plague in 1855. An increase also 

 in the number of small birds does much towards reducing the number 

 of caterpillars, which form to a great extent their natural food. In 

 fact they may have had more to do with the disappearance of Cratagi, 

 than bad seasons. 



It has been mooted that melanism is produced by atmospheric 

 conditions. Be this as it may, it is certain that more rain falls in the 

 North of England, where melanism is most frequent, than in the South. 

 On the average there are 350 days on which rain falls in the North and 

 West of England, against 150 days in the South and East. The Stye 

 Head in Cumberland is reckoned to be the wettest place in England, 

 and Cambridge to be the dryest. Let us take for instance the rainfall 

 of one year, that of 1881. At the Stye Head it amounted 172-56 in. 

 at Cambridge to 18-41 in. A quantity of rain also falls in the New 

 Forest, and in Ireland. On the other hand, brilliant and light colours 

 hold the sway in the sunny South, and especially on the South Downs, 

 the chalk soil of which absorbs a considerable amount of heat favourable 

 to the development of such species as Galathea, Cory don, and Adonis. 

 Lord Walsingham in an address to the readers of the Yorkshire 

 Naturalists' Union in 1885, argues that northern and mountain species 

 of Lepidoptera are dark, because dark colours absorb heat. Is such 

 the case ? I say no ! The dry chalk soils of the south absorb a greater 



