104 BUTTERFLIES 



started the growth of vegetation anew. The insects then 

 make up for lost time and produce several broods in rapid 

 succession. 



In the Imperial Valley of California this butterfly is a 

 serious pest to alfalfa growers. It continues to reproduce 

 throughout a very long season, one brood following another 

 from March until December, and in mild winters there 

 seems sometimes to be practically no cessation of its 

 activities. IVIr. V. L. Wildermuth found that the devel- 

 opment of a generation in breeding cages in this valley 

 varied from twenty-two to forty-four days, the latter in 

 cool, the former in hot weather. The stages in the first 

 and the third broods in spring varied thus: Egg, first six 

 days, third four days; larva, first thirty days, third twelve 

 days; chrysalis, first eight days, third ^ve days. In this 

 case the first generation extended from March 15 to April 

 30 and the third from May 28 to June 20. After the 

 fourth brood of butterflies there was such an overlapping 

 of the various stages that it was impossible to distinguish 

 the broods. 



The Pink-edged Sulphur 



Eurymus interior 



This beautiful butterfly was first made known to the 

 world of science by Louis Agassiz, the great naturalist 

 who did so much to arouse a scientific interest among 

 Americans. He found it on a famous expedition to the 

 northern shores of Lake Superior, which not only served 

 to bring to light many interesting phases of geological 

 history but also laid the foundation for the copper mining 



