AMERICAN DYMKNOrTKRA. 271 



ov more circular row?, one above another. At certain points where, 

 apparently, tlicre is need of especial vomitory, the tiates are much 

 multiplied. Besides these, there are openings at irrcLiuhir intervals 

 upon the entire surface of the cone. These are not nunier(»us. but 

 sutficiently so to allow easy approach to and exit from the more ele- 

 vated portions of the mound. The main dependence appears to be 

 upon the lower gateways. It would seem, at first thought, that there 

 could be no real necessity for so many. doors; but one who has wit- 

 nessed the rapidity with which the myriads of workers swarm upon 

 the surface when their nest is attacked will at once perceive the 

 econoui}' of these numerous gates. The doors are simply the surface 

 openings of the galleries with which they correspond in size. 



Huber declares it to be one of the fixed habits of the fallow ant 

 (F. rufa), of Switzerland to close the gallery-doors at night and re- 

 open them in the morning. Tlie most careful attention could dis- 

 cover no such behaviour among the ants at Camp liiddle. At no 

 time during the whole week was there observed any sign of attempt 

 to close up the galleries. Kven during the heavy storm of rain re- 

 ferred to, the doors which were closely examined at various hours of 

 the night, remained open. It would have been more satisfactory could 

 an observation have been made duriug a fall of rain in the day time, 

 but 1 have little doubt on this point, and none at all on the ordinary 

 night-condition of the doors. This is certainly a remarkable variation 

 in habit. It may po.ssibly be accounted for by the presence in Switzer- 

 land of some nocturnal enemy, from which the American congeners 

 are free. 



Before takitig up in detail the life habits of our mound builders, 

 a comparison and contrast may le alh wed which may give a popular 

 illustration of the immense labors of the i'allow ant. 1 have calcu- 

 lated the cubic contents of one of the largest hills to be. in round 

 numbers, two ujillions of cubic inches. Let us estimate the bulk of 

 an ant equal to that of a cylinder three-eighths of an inch high and 

 one-sixteenth of an inch in diameter at the base. We have thirty-five 

 one hundred thousandths of a cubic inch as the bulk ot a single ant, 

 or two thousand eight hundred and sixty insects to the solid inch. 

 The size of the builder is therefore to the size of the edifice as one to 

 fiffi/-<i<jht thousand millions. Let us compare this with a correspond- 

 ing estimate of the work of man (taking his bulk at f lur cubic feet), 

 as wrought upon the great pyramid, reckoned to contain two hundred 

 and seventy-six millions of cubic feet. 



Miin's bulk to liis builiiing is as 1 : 00 millions. 



Tlie Aiit's bulk to lier building is as I : .jbOU millions. 



