228 LETHARGY 



early in the season a portion of a brood will dis- 

 close the butterfly, while another portion will re- 

 tain the inmates until the succeeding spring. But 

 its occurrence in the active larval stage is far 

 more unexpected. 



This lethargy in caterpillars was first observed 

 by a French naturalist named Vaudouer more 

 than sixty years ago, but his statements lay a long 

 while nearly unnoticed. According to this ob- 

 server (a full account of whose observations is 

 given in my New England Butterflies), one of 

 the European species of Brenthis upon which he 

 experimented flies in May and again in July and 

 August. The caterpillars from the second sum- 

 mer brood are half grown when winter comes, 

 hibernate in this stage, and in time produce the 

 spring brood ; the caterpillars of the spring brood, 

 when they have reached the hibernating age, late 

 in June, act in a precisely similar manner, and 

 some of them do not arouse until the succeedino- 

 spring, when, with the caterpillars of the summer 

 brood, they produce a new spring brood; but 

 other caterpillars of the spring brood, which be- 

 came lethargic, awaken from their torpidity after a 

 time, resume eating, undergo their transformations, 

 and emerge as butterflies in July and August. 



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