244 A COUNTRY READER. 



scendants, at the end of the year there would be 

 in the world, with enormous appetites, feeding 

 as hard as they can feed, 20,000 caterpillars as 

 the descendants of one single butterfly. 



In August, 1876, a swarm of the cabbage- white 

 butterflies about a league broad, was seen flying 

 over a part of Holland, and flying without cessa- 

 tion they took from twelve noon till seven in the 

 evening to pass over. 



This swarm had probably eaten all the food 

 of their own district and had collected together 

 in order to migrate to another district, where 

 their own particular food was more plentiful. 

 The cabbage-white butterfly crawls forth from 

 his pupa or resting-place in 

 the spring, having passed 

 the winter in the chrysalis 

 condition, fixed to a tree 

 trunk or wall. These chry- 

 salises are exposed to ex- 



CABBAGE-WH1TE (MALE). 



treme changes of weather, 

 sun and frost, and this thins them out. Then the 

 nuthatches, wrens, tits, and gold crests feed on 

 them. Also ichneumon flies lay their eggs in 

 them and so bring about their death. 



It is reckoned that out of 100 chrysalises only 

 about 10 survive these winter dangers. 



In the spring some of the caterpillars that are 

 hatched out of the 10 surviving pupae are 



