34^ Bulletin American Museum of Natural History. [Vol, XXII, 



colony under a stone in the Grand Canon just above the Indian 

 Garden (3876 feet.) 



Ph. descrtortmi is allied to Ph. susanncB Forel of the American 

 tropics and Ph. longipes Pergande of Mexico. From susanncB it differs 

 in its larger size, much longer antennae in the soldier and much slighter 

 constriction of the occiput in the worker. Comparison of my speci- 

 mens of dcscrioriim with Pergande's description of the soldier of 

 longipes, with a type specimen of the worker of this species and another 

 worker from San Jacinto, California, given me by Prof. Emery, shows 

 a ntimber of differences. Pergande describes the space between the 

 frontal carinae of the soldier as "quite smooth and faintly shagreened, " 

 the posterior half of the head as having "elongated shallow depres- 

 sions", etc. The worker of longipes, like that of susannce, has the 

 head produced and much constricted in the occipital region and 

 "forming a distinct neck", the long basal surface of the epinotum 

 is distinctly convex, and the petiole is more campanulate than in 

 dcsertoriim. 



9 Myrmica rubra scabrinodis Nylander. — A single colony of a 

 small, dark-colored variety of this subspecies, with rather large, 

 rounded, calyculate lobes on the base of the antennal scapes of the 

 worker and female, was found under a stone in the Kohonino Forest 

 on the rim of the canon. This variety closely resembles a form not 

 uncommon in the mountains of Colorado at a corresponding elevation, 

 and others peculiar to the shady woods and tamarack bogs of the 

 northern States. 



10. Pogononi5nrmex occidentalis Cresson. — The "Occident ant" 

 may be found nesting all the way from Ash Fork and Williams, 

 Arizona, to the Grand Canon, and from the rim of the latter to an 

 altitude of 4000 feet, but not lower. The nests near Ash Fork and 

 WiUiams are large and typical, with great bare areas, often 20 or 30 

 feet in diameter, surrounding their elegant gravel cones, but in the 

 Kohonino Forest and especially on the walls of the canon, they exhibit 

 unmistakable effects of adverse conditions. The absence of horizontal 

 surfaces and the washing of rains have induced the insects to nest 

 under large stones or in crevices of the rock. They still heap the 

 pebbles about the entrance, but the nests are merely caricatures of 

 the fine structures in the plateau region. P. occidentalis is the ant 

 par excellence of the Great Plains. A study of its distribution from 

 Montana, Wyoming and Colorado to Arizona and New Mexico, shows 

 that it is at its best only at an elevation of 6000 to 7000 feet and 

 that it rarely descends below 4000 or 5000 feet. 



