270 HENRY C. MCCOOK. 



that part af the formicary which is above j^round and is apparently 

 the most considerable. There is however a hidden portion which is 

 immense in extent, and must have vas^t importance in the economy of 

 the community. Every hill furnishes a fair measure of the extent of 

 the under<i;round system of <ialleries connected therewith ; for it is 

 reasonably certain that the entire bulk of soil in each mound has been 

 excavated and brouiiht up from the ti'alleries beneath the surface. The 

 average width of the upper galleries is about three-eighths of an inch; 

 the maximum width not exceeding one-half inch. The underground 

 galleries are probably of the same size. A glance at these mounds, 

 therefore, at once gives indication that an extraordinary system of 

 subterraneous galleries must be connected with each formicary, I made 

 no satisfactory examination into the arrangement of this system; this 

 might have been done, perhaps, by sinking a deep trench close to a 

 mound and extending it for some distance. But th« soil is so very 

 full of stones that even thus the results might not be satisfactory. 

 No doubt the ants descend to considerable depths utilizing the stones 

 in various ways, for example for roofs and walls, as they do upon the 

 surfacq^ It would hardly seem possible to preserve any great regu- 

 larity in the course of these underground ways which must constantly 

 be diverted by the stones. But they undoubtedly can be held to a 

 general course, and are carried with great directness from point to 

 point when it is desired to communicate with the trees and feeding 

 places. I was able in one case to trace the extent of the galleries near 

 the surface in the following way. Tapping upon a hill whose inmates 

 were in a particularly " nervous" condition, the ants issued in excited 

 hordes not only from the doors of the mound, but from various points 

 on the surrounding surface. Taking a principal centre of excitement, 

 four or five feet distant, a stone underneath which was an entrance to 

 the galleries, J ngain agitated the ground. The ants as bel'ore issued 

 from the surrounding surface, chiefly upon a line running eastward, 

 up the slope. At the limit of excitement, which was something less 

 than before, I once more agitated the stones and earth with like results. 

 Thus I traced this surface gallery eastward about (JO ft., where the 

 excitement under the above treatment ceased at an oak tree. 1 am 

 satisfied that as a rule the central formicary or hill communicates with 

 the trees which serve for feeding grounds, by galleries as long as or 

 much longer than this. 



Kiilraaii'es or Doors.— The pi-incipal entrances to the firmicary 

 are at the foot of the hill. They are commonly placed around the 

 entire circumference of the mound, and are arranged in two, three. 



