Order RODENTIA 125 



KEY TO SPECIES 

 Whole Animals 



1. Hair at raid-length of tail longer than diameter of tail. . . 2 

 Hair at mid-length of tail shorter than diameter of tail, or 



hair absent 9 



2. Tail not more than ]/^ over-all length of animal; feet black; 



skull more than 70 mm. (2^ in.) long 



woodchuck, Marmota monax 



Tail more than l^ over-all length of animal; feet not 

 black ; skull less than 70 mm. long 3 



3. A large, loose fold of skin between front and hind legs, 



fig. 83 ; bush of tail in cross section decidedly flattened 



southern flying squirrel, Glaucomys voltins 



No loose fold of skin between legs; bush of tail round or 

 oval in cross section 4 



4. Hair at mid-length of tail less than 20 mm. (^ in.) long . 5 

 Hair at mid-length of tail more than 35 mm. (1^ in.) long. 7 



). Body without longitudinal stripes, fig. 78 . . 



Franklin's ground squirrel, Citellus franklinii 



Body with longitudinal stripes 6 



6. Body with 2 longitudinal light stripes bordered with dark 



brown, these stripes represented also on the sides of the 



face, fig. 79 eastern chipmunk, Tamias striatus 



Body with more than 2 longitudinal light stripes bordered 

 with dark brown, no stripes present on the sides of the 



face, fig. 76 



. . thirteen-lined ground squirrel, Citellus tridecemlineatus 



7. Over-all length of animal less than 350 mm. (13)4 i"-) I a 



short black stripe bordering the belly color on each side, 



fig. 80 red squirrel, Tamiasciurus hudsonicusi 



Over-all length of animal more than 350 mm.; no lateral 

 dark stripe bordering belly color 8 



8. Upper parts of animal uniform ffray, under parts gray or 



white ; tail with white-tipped hairs 



eastern gray squirrel, Sciurus carol'inensis 



Upper parts of animal dappled gray, under parts reddish; 



tail with red-tipped hairs 



eastern fox squirrel, Sciurus niger 



9. Claws on front feet, fig. 85, 3 times as large as claws on hind 



feet; each cheek with a pouch that opens by an external, 



curved slit starting near the side of the mouth 



plains pocket gopher, Geomys bursarius 



Claws on front and hind feet subequal in size; no external 



cheek pouches 10 



10. Tail flattened dorsoventrally. fig. 87, more than 50 mm. 

 (2 in.) wide; head+body more than 400 mm. (15f^ in.) 

 long beaver, Castor canadensis 



tThis species probably is not now present in Illinois. 



