STUDIES OF THE NORTH AMERICAN GEOMETRID MOTHS 



OF THE GENUS PERO. 



By John A. Grossbeck, 



Of tin Experiment Station, New Brunswick, New Jersey. 



The genus p ero Herrich-Schaeffer (=Azelina GuenSe in part) 

 lias been a perplexing one to American students, and from the 

 beginning of my studies in the Geometridse I have been gathering 

 material with a view to a revision of the group in so far as it was 

 represented on the American continent north of Mexico. At the, 

 outset three species were recognized, honestarius Walker (the ancetaria 

 of our lists with its variety peplaria), giganteus, new species, then 

 thought to be the occidentalis of Ilulst, and a small western species 

 that was generally regarded as identical with honestarius. Behrensa- 

 rius Packard was not then autopically known to me. There were 

 besides these several puzzling specimens which could not be placed 

 with any of these three forms, and it was only as material accumu- 

 lated that they were set aside as good species in themselves. 



Finally my own collection of one hundred and fifty odd examples 

 was grouped into species to my own satisfaction; slides were made 

 and structures examined, and in all cases these bore out the arrange- 

 ment as based on superficial characters. Before finally revising the 

 genus, however, additional material was sought from all available 

 sources. 



Except for one or two odd specimens the original arrangement 

 remained until the advent of about three hundred specimens from 

 Dr. William Barnes. These specimens from many points in the 

 United States and southern Canada showed a greater distribution of 

 certain of the species, and the farther away from its metropolis a 

 species ranged the more unlike the typical examples it appeared. The 

 work was gone over again with the result that two more new species 

 were discovered ; and, while the distinctness of the other species was 

 not at all rendered questionable, it was found that there existed a 

 greater range of variation than was at first believed. 



Proceedings U. S. National Museum, Vol. 38— No. 1753. 



359 



