80 The Study of Animal Life part i 



tance, produce an effect resembling the flashing of the 

 Aurora Borealis ; sometimes the effect is that of rainbow 

 hues in the spray of laughing waterfalls ; sometimes that of 

 fire ; sometimes that of a smoke-wreath. 1 ' " Each column 

 looks like a kind of slender network, and has a tremulous 

 undulating motion. The noise emitted by myriads and 

 myriads of these creatures does not exceed the hum of 

 a single wasp. The slightest zephyr disperses them." 

 After this midsummer day's delight of love, death awaits 

 many, and sometimes most. The males are at best short- 

 lived, but the surviving queens, settling down, may begin 



Fig. 17. — Saiiba ants at work ; to the left below, an ordinary worker ; to the 

 right a large-headed worker ; above, a subterranean worker. (From Bates.) 



to form nests, gathering a troop of workers, or sometimes 

 proceeding alone to found a colony. 



A caste of workers (i.e. normally non- reproductive 

 females) distinct from the males and queens, involves, of 

 course, some division of labour; but there is more than 

 this. Workers of different ages perform different tasks — 

 foraging or housekeeping, fighting or nursing, as the case 

 may be ; and just as the various human occupations leave 

 marks both for good and ill in those who follow them, so 

 the division of labour among ants is associated with differ- 

 ences of structure. Thus, in the Saiiba or Umbrella Ant of 

 Brazil (CEcodoma cephalotes), so well described by Bates in 



