592 THE BUTTERFLIES OF NEW ENGLAND. 



rest, we have contrasted colors frequently to be met with in the subalpinc 

 region in the latter part of the season when frosts have begun their work. 

 But whether these protective resemblances are very necessary in a district 

 where so few birds are found, hawks and snow birds being almost the only 

 persistent inhabitants, may perhaps be doubted, and the markings which 

 we find on these insects may be only their ancestral inheritance, useful on 

 the arctic barrens where birds are more various and plentiful. The Bren- 

 this indeed seems really doomed to destruction. In the scanty numbers 

 that one may find upon the mountain slopes, one sees the sign of their 

 early departure ; for, in the many years that I have searched for them 

 with special pains, I have never seen more than a dozen or two specimens 

 in a single day. Yet this is not at all true of Oeneis, and one hardly 

 need to be anxious, in our generation at least, concerning its persistence, 

 for the butterfly is as abundant in its native haunts in proper season as 

 almost any of the more favored inhabitants of lower levels. 



BIBLIOGRAPHY. 



See essays by Mr. A. R. Grote in the American naturalist, x : 129, the Canadian entomologist, 

 vii: 164, and Psyche, i: 76, as well as his Illustrated Essay on Noctuidae. See also the papers 

 referred to on p. 134, and Gray's notes on the Alpine floras in the American journal of science 

 1857. 



Table of species of Brenthis, based on the egg. 



Vertical ribs less than twenty in number myriua. 



Vertical ribs twenty or more in number. 



Much more than half the vertical ribs reach the summit montinus. 



Much less than half the vertical ribs reach the summit bellona. 



Table of species, based on the caterpillar at birth. 



Bristles with a slender apical enlargement, the supports of the lateral spicules inconspicuous, 

 scarcely projecting myriua. 



Bristles with a considerable apical enlargement, twice as broad as its neck, the supports of the 



lateral spicules not inconspicuous, giving it a somewhat jagged appearance bellona. 



(Montinus unknown.) 



Table of species, based on the mature caterpillar. 



Laterodorsal tubercles of the first thoracic segment many times longer than the others, my rina. 

 Laterodorsal tubercles of the first thoracic segment scarcely longer than the others. ..bellona. 



(Montinus unknown.) 



Table of species, based on the chrysalis. 



Laterodorsal tubercles of abdomen almost uniformly conical, those of the first segment smaller 

 than those adjoining myrina. 



Laterodorsal tubercles of abdomen constricted beyond the middle, bluntly rounded at tip, those 



of the first segment of the same size as the adjoining bellona. 



(Montinus unknown.) 



