1907.] 
Wheeler, A ISleiv Guest-ant. 
71 
tildes varying from 5,000 to 10,000 feet, I never once saw a 
specimen. During the summer of 1906, however, while collecting 
in Florissant Canon, at an elevation of 8,500 feet, I came upon 
a flourishing colony of M. brevinodis spread out under a group 
of five flat stones on the grassy bank of a stream and containing 
numerous workers, a few callow females and males, and many 
larvae and pupae of a Leptothorax, which, on account of its very 
dark color, I at first took to be an undescribed species. Closer 
examination, however, showed that it might be regarded more 
properly as a subspecies of the New England emersoni. The 
host, too, was found to differ in several minor characters from 
the eastern form of M. brevinodis. A portion of the Florissant 
colony was taken alive and kept for six weeks in an artificial nest 
for the purpose of observing the behavior of the ants. My notes 
on this colony will be recorded below, after a description of the 
new subspecies of Leptothorax and a revision of the varieties of 
M. brevinodis. It was necessary to make this revision in order 
to gain a clearer conception of the taxonomic affinities of the host 
ants to each other and to the other varieties of the subspecies. 
Leptothorax emersoni glacialis subsp. nov. 
The worker measures 3-3.5 mm. in length and differs from the 
worker of the typical emersoni in the following characters : the 
mesonotum is distinctly less convex so that the thorax in profile is 
more like that of L. acervorum, and the hairs are less abundant and 
somewhat more reclinate on the antennae and legs. As in the typical 
form, many of the hairs on the body and tibiae are obtuse, but not 
clavate. The head and gaster are black, the thorax, upper portion of 
the petiole and postpetiole, and the extreme base of the gaster, dark 
brown ; the legs, antennae, clypeus and mandibles are yellowish brown,, 
the clubs of the antennae infuscated. The worker is less variable in 
size, and individuals with ocelli are much rarer than in the typical 
emersoni. 
The female is no larger than the worker and of a very similar 
color, except that in mature specimens the thoracic dorsum is as dark 
as the head and gaster. 
The male measures 3 mm. and is black throughout, except the tarsi 
and articulation of the legs, which are sordid yellow. The mandibles 
