444 REPORT OF NATIONAL MUSEUM, 1893. 



folks of tlie Brazos River and on the Llano Estacado as far south as 

 Canon Blanco (Coi)e, Zool. Pos. Texas, p. 24; Proc. Pliila. Acad. 1892, 

 p. 330). Further west Capt. Pope collected specimens at the Pecos 

 Eivernear the thirty-second parallel. As we leave the plains in going 

 west M'C find this species ascend higher into the mountains, as it is not 

 uncommon in New Mexico and Arizona and Colorado above 5,000 feet 

 altitude. Even in Montana and Idaho it reaches this elevation, at least 

 in places, though it probably does not occur much higher. Although 

 the main divide of the Rocky Mountains in this northern region seems 

 to be the limit of its extension to the west, yet in at least one place 

 where there is no high crest to obstruct its passage across, has it been 

 found on the western slope, viz; at Lemhi, Idaho, in which locality it 

 was collected by parties of Dr. Merriam's Idaho exi)loration party, as 

 recorded by me in North American Fauna, No. 5, p. Ill (1891). 



Habits. — The Prairie Rattlesnake being one of the smaller species, 

 as it seldom reaches a length of over 4 feet with a proportionately 

 slender body, does not seem to be a very dangerous snake. Dr. Allen, 

 as referred to above, found it so common in the region visited by the 

 expedition that several hundred were killed by the different members, 

 yet the only casualty resulting from it was one horse bitten. On the 

 expedition of J 872 not less than two thousand were killed and not a 

 man nor an animal was bitten. Allen also comments ui^oii the fact that 

 they were found abroad quite late in the season, as they were met with 

 quite frequently after several severe frosts had occurred. During July 

 two pairs were found in coitn, indicating the season at which they fjair. 

 Dr. O. P. Hay (Proc. U. S. Nat. Mus., xv, 1892, p. 387), on the other 

 hand, quotes Prof. S, W. Williston as stating that the sexes pair in May. 



Taylor (/. c.) found its food habits similar to those of the Massasauga. 

 It is the species often found in or around the homes of the prairie 

 dogs, where they are most abundantly found during the breeding 

 season of the doj,.^ 



Professor Cope records a similar observation (Proc. Phila. Acad., 

 1892, p. 330) and remarks that the snake protects itself by retreating 

 quickly into the holes of the prairie dogs. The popular belief that 

 these rodents and the rattlesnakes live together because of any special 

 friendship is certainly erroneous, as there can be no doubt that the 

 latter to a great extent feed upon the offspring of the former. 



In addition to the hibernation, which, according to Dr. Coues, lasts 

 about six months, terminating with the loosening of the ground from 

 frost, Dr. Suckley (Pac. R. R. Rep., xii, Pt. iii, p. 290) observed these 

 snakes m a more or less sluggish and stupid condition during the 

 drought of summer, a condition which he calls " aestivation." 



