SUMMER INDUSTRIES 



catching all fish that happen to be enclosed in the 

 circle. On narrow rivers and canals they even 

 divide into two parties, each of which draws up in a 

 half-circle, and both paddle to meet each other, 

 just as if two parties of men, dragging two long nets, 

 should advance to capture all fish taken between 

 the nets when both parties come to meet. As the 

 night comes they fly to their resting-places always 

 the same for each flock and no one has ever seen 

 them fighting for the possession of either the bay or 

 the resting-place. In South America they gather 

 in flocks of from forty to fifty thousand individuals ; 

 some enjoy sleep while the others keep watch, 

 and others again go fishing." 



Shepherding 



Of shepherding, the only clear illustrations are 

 to be found among ants, some of which keep aphides 

 or green-flies, and others scale-insects. This ex- 

 traordinary habit was well known to Linnaeus, 

 who called the aphides the ants' cows (vaccce for- 

 micarum), and it has received considerable attention 

 from many observers. Perhaps it began in the 

 simple fact that the ants and the aphides frequented 

 the same trees, dining, as it were, at the same 

 bountiful table. Then it was discovered that the 

 aphides would yield up some of their " honey- 

 dew " when licked or tickled, and the ants traded 

 on this. Gradually, perhaps, the ants began to 

 take some charge of their cattle, even building 

 " aerial stables " for them on the branches. The 

 ants are accustomed to put their pupae out to be 



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