Contribution from the Bureau of Entomology, L. O. Howard, Chief 

 August 28, 1914. 



THE ALFALFA CATERPILLAR. 



By V. L. WlLDEEMUTH, 



Entomological Assistant, Cereal and Forage Insect Investigations. 



INTRODUCTION. 



The alfalfa butterfly, ffurymus eury theme Boiscl. (fig. 1), is one 

 of the most beautiful and interesting of the group of butterflies 

 known as " t-he yellows " ; beautiful because of its golden and orange 

 colors which contrast so conspicuously with the bright green of 

 alfalfa fields, and in- 

 teresting because of 

 the wide individual 

 variation, extending 

 from the white or al- 

 bino forms to those 

 that are deep or- 

 ange. To the al- 

 falfa grower in the 

 Southwest, however, 

 its chief interest lies 

 in the great destruc- 

 tiveness of the larvse 

 (fig. 2.) One seeing 

 the yellow butter- 

 flies darting here 

 and there over a green alfalfa field would hardly suspect that a few 

 weeks hence they would cause the same field to appear as brown, 

 dead stubble. Yet this is what happens nearly every year to a 

 greater or less degree in the Imperial Valley of California and in 

 the Salt Eiver Valley of Arizona. 



It was not until 1910 that this butterfly was known to entomolo- 

 gists as a serious pest. Previous to that time reports received from 



Note. — This bulletin is especially applicable to the Southwest, where the alfalfa cater- 

 pillar occurs in destructive numbers in irrigated alfalfa fields. 



48305°— Bull. 124—14 1 



Fig. 1. — The alfalfa caterpillar (Eurymus eurytheme) ; Fe- 

 male in the adult, or butterfly stage. One-half enlarged. 

 (Author's illustration.) 



