THE ANTS OR PISMIRES 



by Schnierla. There are four types of raiders — subterranean, 

 arboreal (mainly), terrestrial swarm-raiders and terrestrial 

 column-raiders ; Schnierla's observations were made on the 

 last two types. They differ in the way their raids are 

 organised ; the first makes a swarm which fans out over a 

 considerable area, the second moves in much more compact, 

 narrow columns. 



The ants have a regular alternation of two phases of 

 activity : one which lasts about three weeks during which 

 the nest or " bivouac " is stationary and only a few raids 

 are made, and one which lasts fourteen to seventeen days in 

 which the bivouac is moved almost every day and during 

 which there are several raids each day. This alternation of 

 relative inactivity with great activity depends on the ovi- 

 position-cycle of the queen. She goes through a short phase 

 in which her abdomen becomes greatly distended and she 

 then lays about twenty thousand eggs in a few days. When 

 these hatch and while the brood is growing, the colony is 

 very active and raids are frequent. When the grubs are 

 nearly full grown about two quarts of insect prey are brought 

 in every day. As these grubs begin to spin their cocoons, 

 raiding dies away rather suddenly and the bivouac becomes 

 stationary. Activity begins again just before the new lot of 

 ants emerge from the cocoons. The regularity of their 

 behaviour depends on the regular oviposition-cycle of the 

 queen and on the way in which almost all the brood keep in 

 step with one another during their development. 



It is still not understood how the queen maintains a regular 

 cycle in egg-production. It is clear, however, that though a 

 stationary colony consisting of eighty thousand or more 

 ants could not feed itself for long by raiding, it is not the 

 shortage of food which directly controls their movements. 

 It is rather that the need of food for the growing brood 



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