CARNIVOROUS INSECTS 183 



is composed of a network of silk supported by arched bits 

 of twigs. The larva remains hidden in the funnel, watch- 

 ing for its prey to be caught in the open mouth. The 

 cases were preferably placed at the edge of slight depres- 

 sions in the rocky surface so that the tubular portion was 

 protected from the full force of the current. On' the 

 surface of a rock about eighteen inches in diameter 106 

 of these nets were counted. The larvae of one of the 

 black flies were very abundant in this stream, and were 

 washed into the mouths of these nets, and probably formed 

 the principal food of the Hydropsy che larvae." 



As might be expected, social insects often engage in 

 concerted raids in search of food. This is notably the 

 case with the South American foraging ants of the genus 

 Eciton. They have no fixed abodes, but form temporary 

 resting-places where, presumably, breeding takes place. 

 Little is known, however, of their domestic habits, the 

 identity of their " queens," or egg-laying females, being 

 at present uncertain. The great armies which traverse 

 the forest regions on the banks of the Amazon are made 

 up entirely of sexless individuals, some of which have 

 larger heads and more powerful jaws than others, and 

 are for this reason known as " soldiers." They have no 

 faceted eyes, while some of the forms are quite blind. 

 The habits of the two commonest species of Eciton are 

 graphically described by Bates in the following passage : 

 " When the pedestrian falls in with a train of these ants, 

 the first signal given him is a twittering and restless 

 movement of small flocks of plain-coloured birds (ant- 

 thrushes) in the jungle. If this be disregarded until he 

 advances a few steps further, 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 



