HOW TO KNOW THE BUTTERFLIES 



of plant-lice that are covered with a white woolly- 

 secretion. These little creatures thrust their 

 beaks into an alder stem and suck the juice at 

 their leisure ; they live in compact colonies so 

 that the alder stem looks as if it were wound with 

 wool. The little butterfly mother selects a stem 

 so infested and lays her eggs upon it ; from these 

 eggs hatch wee caterpillars that start at once 

 on their career of slaughter. When among the 

 aphids the caterpillar weaves about itself a silken 

 covering to protect it from being trod upon by 

 the aphids and to provide a secure place for molt- 

 ing ; to this silk the wool of the destroyed aphids 

 clings and completely hides from view the little 

 butcher. When not among the aphids and passing 

 from one colony to another it spins no such tube to 

 cover itself. If the alder stem is jarred the cater- 

 pillar will detach itself from the mass of aphids and 

 drop to the ground ; or let itself down for a lit- 

 tle distance by a thread of silk, a habit not com- 

 mon among butterfly caterpillars. Perhaps it 

 does this to save itself from its inveterate foes, the 

 ants, which attack fiercely any depredator they 

 find working havoc with their flock of milch 

 cows, the aphids. It seems to be to escape the ants 

 that this caterpillar hurries through its life stages, 

 molting only three times. The chrysalis looks 



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