60 CEREAL AND FORAGE INSECTS. 



HISTORY AND EXTENT OF THE OUTBREAK IN NEW MEXICO. 



As has just been stated, the first information that reached the 

 United States Department of Agriculture at Washington concerning 

 the alarming increase of Hemileuca caterpillars in New Mexico came 

 in August, 1908. A letter from Mr. Frank Springer, one of the owners 

 of the large Springer ranch that lies between the villages of Springer 

 and Cimarron in Colfax County, was forwarded to Washington by 

 Prof. T. D. A. Cockerell, to whom it was addressed. This letter 

 contained a brief account of the damage then being done to range 

 pastures in the vicinity of Springer by legions of caterpillars that 

 had apparently been increasing in numbers for several years. Mr. 

 Springer stated his belief that, unless checked in some way, these 

 pests threatened to become a serious menace to the cattle-raising 

 industry of northern New Mexico. 



The interest aroused by this presentation of somewhat startling 

 facts resulted in a careful study of the depredating species covering 

 the adult period of the insect in 1908 and the entire active life period 

 of 1909. 



The history of the range caterpillar prior to the outbreak of 1908 

 is exceedingly vague, and the information obtained from ranchmen 

 and others is very unreliable, probably owing to the fact that they 

 have not been able to distinguish clearly between these caterpillars 

 and those of other species. A notable illustration was offered dur- 

 ing the year 1909. There was a severe outbreak of the wheat-head 

 army worm (HeliopJiila albilinea Hiibn.) in northern New Mexico, 

 which took place simultaneously with the occurrence of the Hemileuca 

 larvae, while in many cases reports current through the country at- 

 tributed all of the ravages to the range caterpillar. In view of what 

 we have learned since taking up the investigation of the range cater- 

 pillar, it would seem that the species might have had its origin in the 

 country east of and adjacent to the Rocky Mountains in northeastern 

 New Mexico. The information relative to the occurrence and food 

 habits of closely related species is as yet too meager to throw much 

 light upon this problem. It is possible that there have been previous 

 outbreaks of this particular species of Hemileuca, but if so the evi- 

 dence is too meager and obscure to permit of any definite statement 

 to that effect. The extremely limited extent to which the range 

 caterpillar is affected by natural enemies is of itself somewhat puzzling 

 and would rather indicate that if there had been previous outbreaks 

 these were overcome, if at all, very slowly, by. natural enemies. If 

 all of these questions were capable of prompt solution, we might have 

 a basis for estimating the probable extent to which the pest will 

 spread over adjoining country; with our present knowledge, how- 

 ever, it will require at least another season to determine whether the 

 species will retain its foothold in adjacent States to the north and 



