THE NEW MEXICO EANGE CATERPILLAR. 



81 



Where weeds are not available for pupation, clumps of grass are 

 used, their stems being often drawn together by a mass of webs until 

 they resemble in shape an Indian tepee. When both weeds and 

 grass stems are wanting, the larvae burrow under the short grass 

 close to the ground and draw the blades together for what little pro- 

 tection they will afford. 



The silk spun into these cocoons is of a dirty white or even brownish 

 color, and is always 

 lumpy and uneven. 



The number of 

 pupae that are packed 

 away in the weeds in 

 the manner above 

 described is almost 

 incredible. The so- 

 called ' ' snake- weed ' ' 

 or ' ' sheep weed ' ' (Gu- 

 tierrezia |sp.), com- 

 mon everywhere on 

 the range and a favor- 

 rite plant for both 

 oviposition and pu- 

 pation, has been ob- 

 served packed so full 

 of pupae that from a 

 plant that could 

 easily be contained in 

 a quart measure more 

 than fifty pupse have 

 been taken. (See 

 fig. 45.) 



During September, 

 1909, large areas, cov- 

 ering many square 

 miles, were observed 

 in which all the weeds 

 and bunches of coarse 

 grass were literally 

 filled with the cocoons and pupse of the Hemileuca. When the 

 moths emerged in such locations they swarmed in countless numbers 

 at dusk. 



Previous to the season of 1909 nothing was known definitely con- 

 cerning larval or pupal history, and no dates could be given. August 

 18, 1909, a larva was found in the vicinity of Koehler, N. Mex., 

 beginning to spin its cocoon, the earliest example seen during that 



Fig. 45.— The New Mexico range caterpillar: A charasteristic mass of 

 cocoons in a single plant of Gutierrezia. Reduced. (Original.) 



