10 



BULLETIN 443, U. S. DEPARTMENT OF AGRICULTURE. 



HISTORY OF THE RANGE CATERPILLAR. 



As a result of complaints received from the stockmen of north- 

 eastern New Mexico concerning the ravages of the range caterpillar, 

 a preliminary investigation was made during the period 1908 to 1912. 1 



It appears that no records exist of damage by this insect until 

 about 1904 — that is, five years previous to the beginning of the original 

 investigations. There is no doubt, however, that the range cater- 

 pillar has been present in limited numbers in the section for many 

 years, and probably for centuries. Taking these facts into consid- 

 eration, it is probable that just previous to the date mentioned above 

 some severe and unusual climatic condition caused the death of most 



Fig. 11.— Pimpla conquisitor, a parasite of the range caterpillar: a, Larva; b, head of same; c, pupa; d' 

 adult female. Enlarged, {d, C. N. Ainslie; a, b, c, redrawn from 4th Rpt. U. S. Ent. Comm.) 



of the natural enemies of the range caterpillar but allowed the pest 

 to survive, and in consequence to multiply rapidly and injure the 

 range. These unusual climatic conditions might have been in the 

 nature of a severe, long drought, or it might have been a mild, warm 

 period in midwinter, followed by a rapid drop in temperature, con- 

 ditions which occur in the plateau regions of New Mexico. 



In 1913 a camp was established in the midst of badly infested range 

 pastures on the open range 6 miles east of Koehler, N. Mex. To 

 this camp natural enemies of the range caterpillar were brought 

 from various parts of the country. Experiments carried on under 

 temporary structures demonstrated that some of these natural ene- 

 mies were effective against the pest and were capable of existing 



1 Ainslie, C. N. The New Mexico Range Caterpillar. U. S. Dept. Agr. Bur. Ent. Bui. 85, pt. 5, 

 pp. 59-96, figs. 32-53, pis. 3, 4. 1910. 



