Peatjody Academy of Science, 



Salem, Mass'., August 10, 1S75. 



Dear Sir : I beg leave to transmit to von a moiiograpliical account of 

 the North Ainerican species of Geoinelrid moths. The material which was 

 collected hy Lieut. W. L. Carpenter, in Colorado, in 1873, while attached to 

 yonr party, and hy others in the same l^erritory, added to extensive collec- 

 tions received from the I'acitic States, as well as the Atlantic States, have 

 made me anxious to treat tlic snhjfTt more thoroughly, and eidarge iipon tlie 

 slight sketch pul)lished in your Annual Report for 1874. 



That I can do this in the jjresent fonn is (Uk; to your enlightened inter- 

 est in the connection of biological with geological and geographical science. 

 By an attentive study of the insect fauna of the plateaus and mountains ol 

 Colorado and adjoining Territories, we are led to comparative studies of tin' 

 piiysical features of those regions with the elevated plateaus of Asia. Tin; 

 com[)aratively ll'w specimens ])reviously received from Colora(h> indicate a 

 similarity in its fauna to the Ural aiul Altai ]\Iountains. most striking and 

 unexpected to myself, and perhaps to most persons. 



Besides the relations to comparative physical geography and the; geo- 

 graphical distribution of animals, it is l)elieved that an extended exandnation 

 of th'e existing insects of the Western States and Territories will throw light 

 on the extinct forms which al)ound in the Tertiary formation in those regions, 

 and which have been jwrtially worked up by Mr. S. H. Scudder, the eminent 

 palentoniologist, on materials discovered within the limits of Colorado and 

 Utah. For this purpose in part, at least, much attention has been devoted 

 in the illustrations accompanying this rep-ort to the venation (if the wings of 

 each genus of the family, as well as to Ihe anatomy of file hard parts of these 

 insects which are more likely to be preserved fossil. 



From an economical point of view, a systematic account of the species 



of this family, comprising the measuring or span worms, so many of which 



are injurious to vegetation, will.it is hoped, prove useful to agriculturists; 



and it is Ijolieved that a volume on these injurious insects, largely represented 



1 p II 



