NEW MEXICO RANGE CATERPILLAR AND ITS CONTROL. 



covered with clusters of sharp, poisonous spines. They remain in this 

 stage about four weeks, and, owing to their large size, greediness, and 

 great numbers, do their greatest damage at this time by devouring, 

 or rendering unfit for grazing, most of the range grasses, and certain 

 cultivated crops to a more limited degree, over large areas. 



WHERE THE RANGE CATERPILLAR OCCURS. 



At the present time the range caterpillar is known to occur in the 

 northeastern and south-central portions of New Mexico, with a 

 scattering infestation along the adjoining "Pan- 

 handle" of Texas. During the season of 1915 

 small colonies were found at Duran and Corona, 

 in southern New Mexico. The parent moths have 

 been found outside the limits mentioned, but in 

 these localities no caterpillars have ever been dis- 

 covered, although the surrounding country has 

 been searched each year for evidence of their 

 presence. It seems possible that this pest may 

 eventually be found far to the southward of its 

 present known limits, but the insect is now of 

 great economic importance only in the north- 

 eastern corner of New Mexico, in the counties of 

 San Miguel, Taos, Mora, Colfax, and Union. 



ITS ECONOMIC IMPORTANCE AND GREAT ABUN- 

 DANCE. 



Fig. 3.— The New Mexico 

 range caterpillar: Lar- 

 vae clustered on weed 

 stem, to avoid the 

 heated surface of the 

 ground. (C.N. Ainslie.) 



In many parts of the section just mentioned 

 these range caterpillars, or " grass-worms," as 

 they are popularly known, constitute a great 

 menace to successful stock raising and farming. 

 When the present investigations began, many 

 stockmen and farmers were of the opinion that on 

 account of the ravages of this insect it would be 

 necessary to abandon stock raising in that part of New Mexico, 

 which, as has been stated, includes an area of approximately 30,000 

 square miles, or about the area of Maine. 



Owing to the constantly decreasing area devoted to stock raising, 

 the economic importance of this caterpillar can not be overestimated. 



The great abundance of these caterpillars should be taken into 

 consideration in estimating the damage caused by the insect. In 

 1913 a total of 300 full-grown caterpillars were counted feeding upon 

 an average square rod of pasture, 6 miles northeast of Las Vegas. 

 This is at the rate of 30,720,000 of these large caterpillars per square 

 mile. Many square miles in this section were similarly infested. 

 The caterpillar is commonly found in numbers of from 100 to 200 



