2 BULLETIN 443^ U. S. DEPAETMENT OF AGRICULTURE. 



pillar. Without these natural checks the caterpillar multipHed and 

 became destructively numerous. At the present time the introduced 

 and native natural enemies are apparently reducing its numbers and 

 it is hoped that it will soon cease to be a menace. 



GENERAL DESCRIPTION OF THE RANGE CATERPILLAR. 



The newly hatched caterpillars (fig. 2) are one-fourth of an inch 

 long, dark brown or black in color, covered with fiine prickles or 

 spines, and may be seen during the cooler parts of the day feeding 

 in groups. When not feeding, or during cold or wet weather, the 



Fig. 2.— Hatching of the eggs of the New Mexico range caterpillar. Size of larvae indicated by metric 



rule beneath. (C. N. Ainslie.) 



small caterpillars (fig. 3) ascend a grass or weed stem and twine 

 themselves together in a tight ball, for mutual warmth and protection 

 against cold or rain. When in this position they are conspicuous 

 objects upon the prairie. These small caterpillars feed upon their 

 various food plants, growing rapidly larger, and as this occurs they 

 separate from one another, and generally feed alone. In this process 

 of growth the caterpillar "sheds its skin," or molts, five times, after 

 each molt becoming larger and of a different color, gradually chang- 

 ing from the dark brown or black of the newly hatched caterpillars 

 to a uniform light brown, then to a light brown streaked with yellow, 

 and finally the full-grown caterpillars appear, yellow in color, with 

 faint black markings. These full-grown yellowish caterpillars are 

 from 2 to 3 inches long and as thick as a man's little finger, being 



