200 INSECTS AFFECTING FIELD CROPS 



Dean suggests, the field may be " beaten" with branches by a 

 line of men or children, driving the beetles before them to the 

 edge of the field where rows of dry hay or straw have been pre- 

 viously placed. The insects will run beneath these rows for shelter 

 and may then be destroyed by burning. 



The Alfalfa Caterpillar (Eurymus eurythene Boisd.). The 

 sulfur-yellow butterfly producing the alfalfa caterpillar is common 

 practically over the entire United States and the southern part of 

 Canada. It is an insect familiar to almost all young collectors. 

 The wing expanse is about two inches. 



Description. The black band on the wings of the female is 

 more or less dotted with white, these dots being absent in the male. 

 There is a prominent black dot in the center of the fore-wing, 

 and a pale yellow spot in the center of each hind-wing in both 

 male and female. 



Life History. The small, spindle-shaped eggs are laid on 

 green alfalfa. These hatch into dark-green worms, about one 

 inch long when full grown, with a light stripe on each side, inter- 

 rupted by black and red dots. The chrysalis is greenish yellow, 

 and is attached, head up, by two threads to a stalk of alfalfa or 

 to weeds and grasses. The winter is passed in this stage. It 

 probably has two or three broods. 



Injury. This insect is extremely abundant in the West where 

 large fields of alfalfa occur, and it is a serious pest to this crop. 

 This is particularly true in California, Arizona, and other parts 

 of the Southwest. 



Enemies. A contagious intestinal disease, resembling some- 

 what in effect flacherie of the silkworm, may be in part responsible 

 for keeping this butterfly in check in portions of California and 

 Arizona (Circular 133, U. S. Bureau of Entomology). 



The caterpillar is preyed upon by Tachina flies and by 

 hymenopterous parasites. The cotton boll worm is also said to 

 attack it. 



Control. Pasturing the affected fields is recommended. Also, 

 keep the soil in the best cultural condition. Irrigate frequently, 

 and immediately after the crop has been cut and the hay removed. 

 Renovate by disking. Cut the alfalfa close to the ground, and cut 

 earlier than the general rule. Always cut a few days before it is 

 in blossom, Turkeys and chickens, if allowed to run in the fields, 

 will reduce the number of caterpillars. Cooperation on the part 

 of all farmers in an infected district is necessary. 



