142 SEASONAL CHANGES AND HISTORIES. 



easily divine what complication might ensue 

 through some modification of such a phenomenon. 



But this feature is most curious when it affects 

 the active stages of an insect's life. Beyond the 

 torpidity of winter, we do not know that such a 

 phenomenon occurs in the perfect stage ; but it is 

 by no means an uncommon occurrence among 

 caterpillars, although, so far as we know, it does 

 not happen outside of certain limited groups. In 

 some cases it is simply premature hibernation ; 

 in others it is pure lethargy, the caterpillar 

 affected by ifc awaking from its torpidity during 

 the same season and resuming its active glutton- 

 ous life, as if nothing had happened. 



One of the most extraordinary cases occurs 

 among the fritillaries, and was first observed by 

 a French naturalist, Vaudouer ; according to this 

 observer, one of the European fritillaries upon 

 which he experimented flies in May and again in 

 July and August ; the caterpillars from the sec- 

 ond summer brood are half grown when winter 

 comes, hibernate in this stage, and in time pro- 

 duce the spring brood ; the caterpillars of the 

 spring brood, when they have reached the hiber- 

 nating age, late in June, act in a precisely similar 

 manner, and some of them do not arouse until 

 the succeeding spring, when, with the caterpillars 

 of the summer brood, they produce a new spring 

 brood ; but other caterpillars of the spring brood, 



