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THE POPULAR SCIENCE MONTHLY. 



faceted or compound structure, such as are usual in insects, and 

 which ordinary ants [Formica) are furnislied with ; but all are pro- 

 vided with organs of vision, composed each of a single lens. Con- 

 necting them with the utterly blind species of the genus, is a very 

 stout-limbed Eciton, the FJ. crassicornis, whose eyes are sunk in deep 

 sockets. This ant goes on foraging expeditions like the rest of its 

 tribe, but it avoids the light, always moving in concealment under 

 leaves and fallen branches. When its columns have to cross a cleared 

 space, the ants construct a temporary covered way with granules of 

 earth, arched over, and holding together mechanically ; under this the 

 procession passes in secret, the indefatigable creatures repairing their 

 arcade as fast as breaches are made in' it. 



Next in order comes the JS. vastator, which has no eyes, though 

 the collapsed sockets are plainly visible ; and, lastly, the M erratica^ 

 in which both sockets and eyes have disappeared, leaving only a faint 

 ring to mark the place. The armies of JE. vastator and E. erratica 

 move wholly itnder covered roads, constructing them rapidly as they 

 advance. The column of foragers pushes forward, step by step, under 

 the protection of these covered ways, and, on reaching a rotten log, 

 or other promising hunting-ground, pour into the crevices in search 

 of booty. The grains of earth for their arcades are taken from the 

 soil over which the column is passing, and are fitted together without 

 cement. 



MmUh\ 



Fig. 5. Foraging- Ants {Eciton erratica), constructing a Covered Eoad Soldiers Ballyiug out 



oil being disturbed. 



Working in numbers, they build up simultaneously the sides of 

 their convex arcades, and contrive in a surprising manner to approxi- 

 mate them and fit in the key-stone without letting the loose, unce- 

 mented structure fall to pieces. There is a very clear division of 

 labor between the two classes of neuters in these blind species. When 

 a breach is made in one of their covered ways, all the ants underneath 

 are set in commotion, but the worker-minors remain behind to repair 

 the damage, while the large-heads issue forth in a most menacing 

 manner, rearing their heads, and snapping their jaws with an expres- 



