BULLETIN OF THE 
ffllM 
No. 124 
Contribution from the Bureau of Entomology, L. O. Howard, Chief 
August 28, 1914. 
THE ALFALFA CATERPILLAR. 
By V. L. WlLDERMTJTH, 
Entomological Assistant, Cereal and Forage Insect Investigations. 
INTRODUCTION. 
The alfalfa butterfly, Eurymus eury theme Boisd. (fig. 1), is one 
of the most beautiful and interesting of the group of butterflies 
known as " the 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 larvae 
(fig. 2.) One Seeing Fig. I.— The alfalfa caterpillar {Eurymus eurytheme) ; Fe- 
the vellow butter- male in the adult » or butterfly stage. One-half enlarged. 
" , (Author's illustration.) 
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 River 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 
