2 og NATURAL HISTORY. 



short distance, and then turning again to follow the same course as the 

 main body. But these rearward movements were going on continually 

 from one end to the other of the line, and there was every appearance 

 of this being a means of keeping up a common understanding amongst all 

 the members of the army, for the retrograding ants stopped very often for 

 a moment to touch one or another of their onward-moving comrades with 

 their antenna?, a proceeding which has been noticed in other ants, and is 

 supposed to be their mode of conveying intelligence. When I interfered 

 with the column or abstracted an individual from it, news of the disturb- 

 ance was very quickly communicated to a distance of several yards toward 

 the rear, and the column at that point commenced retreating. . . . 



" The position of the large-headed individuals in the marching column 

 was rather curious. There was about one of these extraordinary fellows 

 to about a score of the small class ; none of them carried anything in their 

 mouths, but all trotted along empty-handed, and outside the column at 

 pretty regular intervals from each other, like subaltern officers in a march- 

 ing regiment of soldiers. It was easy to be tolerably exact in this obser- 

 vation, for their shining white heads made them very conspicuous among 

 the rest, bobbing up and down as the column passed over the inequalities 

 of the road. I did not see them change their position or take any notice 

 of their small-headed comrades marching in the column; and when I dis- 

 turbed the line, they did not prance forth or show fight so eagerly as the 

 others. These large-headed members of the community have been con- 

 sidered by some authors as a soldier-class, like the similarly armed caste 

 in the termites ; but I found no proof of this, at least in the present 

 species, as they always seemed to be less pugnacious than the worker- 

 minors, and their distorted jaws disable them from fastening on a plane 

 surface like the skin of an attacking animal. I am inclined, however, to 

 think that they may act, in a less direct way, as protectors of the commu- 

 nity ; namely, as indigestible morsels to the flocks of ant-thrushes which 

 follow the marching columns of these Ecitons, and are the most formid- 

 able enemies of the species. It is possible that the hooked and twisted 

 jaws of the large-headed class may be effective weapons of annoyance when 

 in the gizzards or stomachs of these birds, but I unfortunately omitted to 

 ascertain whether this was really the fact." 



Some of these foraging ants were blind, and between these and the 

 eyed species the gradations could readily be traced. First are forms in 

 which the eyes are sunk in deep sockets ; next come those with the sockets, 

 but with the eyes gone ; and lastly, those in which both eyes and sockets 

 have disappeared, only a faint ring remaining to show the place where they 

 should be. These blind forms travel in covered ways which are con- 



