viii INTKODUCTION. 



phorus, Wallengren, and even in Lioptilus, Hiibner, 

 this difficulty especially presents itself. 



The Californian and Oregonian specimens of Am- 

 blyptilus certainly include examples which correspond 

 precisely with European specimens of A. acantho- 

 dactylus and A. cosmodactylus respectively ; and Prof. 

 Zeller informs me that he has bred these two forms 

 in Europe from larvae feeding on the same plants 

 of Aquilegia and Geranium pratense, but that he 

 omitted to take the necessary pains to make out their 

 characters in the larval stage. 



My specimens of the genus (Edematophorus^ vary- 

 ing in size and colour between the two extreme 

 forms represented by those hereinafter described as 

 CE. grisescens and (E. guttatus, include several varieties 

 showing a gradual approximation in opposite direc- 

 tions to the intermediate species known as (E. creti- 

 dactylus, Fitch; and some of these can scarcely be 

 distinguished from the European (E. lithodactylus, 

 Treitschke; yet if this last species is not to be 

 confounded with cretidactylus (and it has certainly 



