30 BULLETIX 1091, U. S. DEPARTMEXT OF AGEICULTURE. { B"'un.^So;\\ 



While there is greater complexitj^ in the larger, and piobablv 

 older, mounds than in the smaller, all are extremely complicated and 

 can only be described as labyrinthine in character. The tunnels wind 

 about through the mound, rising and falling in vertical depth, inter- 

 communicating frec[uently, but with occasional cul-de-sacs, and in 

 jilaces expanding into chambers, of which there may be three or four 

 large ones. The stored materials are found in some, but not neces- 

 sarily all. of these chambers, and may also occupy considerable 

 lengths of ordinary tunnel, especially when the quantity present is 

 large. Small evaginations of the tunnels frequently contain lesser 

 caches, and it is in such pockets that bits of fresh material are placed 

 during a growing season, or that grain supplied the previous night 

 for bait is usually found. 



The main masses of storage are most often found centrally located 

 at depths of from 15 to 57 centimeters, although at times one may 

 find a cache near the periphery of the system and as near the surface 

 as 2 or 3 centimeters. In the latter case the materials are subject to 

 wetting from rains, and consequent spoilage. 



The major portion of the whole tunnel system is within about 

 50 centimeters of the surface of the mound, but usually some one 

 branch tunnel goes to somewhat greater depth, and this is likely to be 

 the one containing the nest : this is also likely to extend toward or 

 beyond the periphery of the main system, and always ends blindly. 

 Such a one, from which two young were taken on January 31. 1920. 

 was at a depth of about 65 centimeters, and about 1^- meters beyond 

 the periphery of the mound itself. 



The individual tunnels average about 8 centimeters in height, and 

 about 11 centimeters in width, though the A'ariation. especially in 

 width, is considerable. The expansions mentioned as being the chief 

 places of storage are from 15 to 25 centimeters in diameter, and 

 may or may not involve a considerable increase in height. They are 

 frequently located at junction points of two or more branches of tlie 

 tunnel system. 



The nest cavity is a chamber of aj^proximately spherical shap^i 

 and from IT to 23 centimeters in diameter. Chambers of this 

 character were observed and noted as " old storage " in a numl^er of 

 cases. They were sometimes cut off from the rest of the habitation, 

 and at first were supposed to contain abandoned musty storage. As 

 experience in excavating and interpreting results has been gained 

 we have concluded that these chambers in fact represent abandoned 

 nests. 



Bailey gives the dimensions of nest cham])ers observed in Xew 

 Mexico as about 6 by 8 inches to 8 by 10 inches. The nest is com- 

 posed of finer, softer, and more chaffy material than the regular 



