64 



PROCEEDINGS OP THE ACADEMY OP 



[1884. 



t 



listening to some observations upon the Occident ant — for Mr. 

 Russell spoke of the insects by their popular name of " stinging 



ants " — awakened my 

 suspicion. I knew that 

 amass of gravel-covered 

 dirt, such as the genuine 

 stinging ants — the Occi- 

 dents — heap up, would 

 not melt away in such 

 wise before a prairie-flre. 

 A few questions satisfied 

 me that I was on the 

 wrong trail, and that no 

 other ant than Formica 

 rvfa could build a nest 

 ' ' 1 i ' ^ liable to such an acci- 



' '^ dent, and that even she 



could do so I confess I 

 seriously doubted. 

 \ I had no reason to dis- 



pute the veracity of my 

 , ' informant, but I thought 



5 • «' > < ' it quite as well to test 



J' ,^ I 5 h \\ his statements. Accord- 



I'l ''^. , '^ » = ^^ ' J' ^ ]]■• ingly I had Dr. De Puy 

 {^ '1 ^ '< ' '' send me samples of the 



' I ' ^ material of the mounds 



^ „ ^ at points below the sur- 



FiQ. 5. Half section of mound of F. rufa, 4 ft. 4 in. 

 below surface. B, central ball of sticks and straws; face. The rCSultS I have 

 SigiSi galleries; n, network of crossing galleries just 



below the ball ; G, gates. already mentioned, and 



they show that Mr. Russell's statement is entirely credible. The 

 heavy thatch of dried grass upon the roof, the mixture of soil 

 and decayed straw which composes the cone, the faggot-ball at 

 the heart of the hill, together make up a highly inflammable 

 mass. This freely feeds the flames that eat into the subsoil of 

 the prairie, which is decomposed clay and lime. Thus the story 

 of a casual lay observer, which might have been rejected with 

 apparent reason, was confirmed by careful examination. 



The mounds exposed to these prairie-fires are frequently pre- 

 served from destruction in a rather remarkable way. A narrow 



