CARNIVOROUS INSECTS 105 



works on natural history. It should further be noted that in most 

 ants, as also in bees and wasps, the females and workers (which 

 are really undeveloped females) possess a poisonous sting in the 

 hinder-part of the body. This consists essentially of a couple 

 of slender-toothed stylets, enclosed in a sheath, and connected 

 with a poison-gland, of which the secretion contains formic acid, 

 a substance which indeed owes its name to the fact that ants are 

 the source from which it was first derived (Lat. formica, an ant). 

 Bates speaks as follows of the two commonest species of these 

 Foraging- Ants {Eciton hamata and E. drepanophord): — "These 

 Ecitons are seen in the pathways of the forest at all places on 

 the banks of the Amazons, travelling in dense columns of countless 

 thousands. . . . When the pedestrian falls in with a train of these 

 ants, the first signal given him is a twittering and restless move- 

 ment of small flocks of plain-coloured birds (ant-thrushes) in the 

 jungle. If this be disregarded until he advances a few steps farther, 

 he is sure to fall into trouble, and find himself suddenly attacked 

 by numbers of the ferocious little creatures. They swarm up 

 his legs with incredible rapidity, each one driving its pincer-like 

 jaws into his skin, and with the purchase thus obtained, doubling 

 its tail, and stinging with all its might. . . . The errand of the 

 vast ant-armies is plunder. . . . Wherever they move, the whole 

 animal world is set in commotion, and every creature tries to get 

 out of their way. But it is especially the various tribes of wingless 

 insects [and other arthropods] that have cause for fear, such as 

 heavy-bodied spiders, ants of other species, maggots, caterpillars, 

 larvae of cockroaches, and so forth, all of which live under fallen 

 leaves or in decaying wood. The Ecitons do not mount very 

 high on trees, and therefore the nestlings of birds are not much 

 incommoded by them. The mode of operation of these armies, 

 which I ascertained only after long-continued observation, is as 

 follows : — The main column, from four to six deep, moves forward 

 in a given direction, clearing the ground of all animal matter, 

 dead or alive, and throwing off here and there a thinner column 

 to forage for a short time on the flanks of the main army, and 

 re-enter it again after their task is accomplished. If some very 

 rich place be encountered anywhere near the line of march, for 

 example a mass of rotten wood abounding in insect larvae, a delay 

 takes place, and a very strong force of ants is concentrated upon 

 it. The excited creatures search every cranny, and tear in pieces 



