587 



to study West Indian, Central American, and even tropical South American 

 forms, several members of which spread as far north as the headwaters of 

 the Mississippi, and even Maine and Canada. 



The facts presented in the body of this work regarding the variation in 

 size between Atlantic and Pacific coast examples of the same species, though 

 scanty, indicate the existence of some interesting laws of climatic variation, 

 which tend to confirm the generalizations established by Professor Baird * 

 and Messrs. Allen and Ridgway as regards the avifauna of North America. 

 I should, however, state that the fact of variation in shape of the wings, 

 chiefly, however, variation in size, was forced upon me by a study of the speci- 

 mens themselves, without at the time having the views of our ornithologists 

 in mind. In all the species enumerated in the following list, the Colorado 

 examples (when the species have been found to occur there) and the Pacific- 

 coast individuals are larger, and in some cases with longer, more pointed 

 wings than in those from Labrador or the Eastern Atlantic States, and in a 

 few cases show a tendency to become lighter in color. 



SPECIES GROWING TO A GREATER SIZE ON THE PACIFIC THAN ATLANTIC COAST, f 



Grlaucopteryx csesiata. Zerene catenaria. 



magnoliata. Phasiane orillata. 



Plemyria fluviata. Semiothisa californiata. 

 Hydriomena californiata. granitata. 



Petrophora truncata. Aplodes rubrifrontaria. 



prunata var. lugu- Geometra iridaria. 



brata nubilata. Tephrosia canadaria. 



Ochyria munitaria. Opisthograptis sulphuraria. 



abrasaria. Anagoga pulveraria. 



Rheumaptera basaliata. Metrocampa perlaria. 



lugubrata. Merina fervidaria. 



Hydria undulata. Endropia bilinearia. 



Triphosa dubitata. Azelina hiibnerata. 



* " The Distribution and Migrations of North American Birds," iu Amer. Jonru. Sc. and Arts, xii, 

 Jan. and March, 1866. See also J. A. Allen, Bull. Mus. Comp. Zool., ii, 1871, " On Individual and Geo- 

 graphical Variation among Birds, &c." ; and R. Ridgway, " On the Relation between Color and Geograph- 

 ical Distribution in Birds as exhibited in Melanism and Hypercbromism," iu Amer. Journ. Sc. Arts, iv, 

 Dec, 1872, p. 454 ; v, Jan., 1873, p. 39. 



t To this list may be added the following species belonging to other families of moths : Phrophorus 

 cinvreidactylus, Drasteria ei-echtea, Plusia Hochenwarthi, Agrotis islandka, and Lillwsia argillacca. 



