THE NEW MEXICO RANGE CATERPILLAR. 93 



been observed at one time feeding on a single larva, but only a com- 

 paratively small percentage of the larvae are infested. These mites 

 are, of course, shed with the molted skin, but they are quite active 

 and soon regain a new location on some near-by host. It is probable 

 that they are merely a source of some irritation to their hosts and do 

 them no particular injury. 



ANTS FOUND IN PUPAL SHELLS. 



Empty pupal shells are occasionally found on the infested parts 

 of the range swarming with very minute glistening ants that are 

 quite sluggish in their movements. There is no indication that these 

 ants ever attack perfect pupae, but probably they act merely as scav- 

 engers when a pupa is thrown from its web and broken. These ants 

 appear to be somewhat common everywhere throughout New Mexico. 

 Specimens were submitted to Dr. W. M. Wheeler and determined as 

 Monomorium minutum Mayr, var. minimum Buckley. 



BIRDS. 



On July 27, 1909, two robins were seen, each with a Hemileuca 

 larva in its bill. The birds flew away with these in the direction of 

 shrubbery along Cimarron Creek, as if intending to feed the cater- 

 pillars to their young. The next forenoon it was learned by the aid 

 of a field glass that several robins were busy in that vicinity, not only 

 carrying the worms across the fields, but occasionally eating them. 

 A close watch was maintained on meadow larks, blackbirds, and sev- 

 eral other species of birds, but none of these was seen to attack or feed 

 upon the caterpillars. Robins are not at all numerous in north- 

 eastern New Mexico and are a very small factor in the control of the 

 Hemileuca throughout the infested district, especially as they seem 

 to feed only on the smaller larvae. The spines of the larger larvae are 

 capable of producing much greater urticating effect and are possibly 

 disagreeable to the birds on that account. 



EFFECTS ON THE RANGE CATERPILLAR OF PASTURING. 



Infested pastures have as a rule very few cattle during the larval and 

 pupal periods of Hemileuca life, for the large herds of the region are 

 kept in the mountain pastures through the summer and brought to 

 the lower levels late in the fall to eat the sun-cured grass during the 

 winter. In some cases, however, cattle and horses pasture the low 

 mesas in the summer time and do the Hemileucas some harm, espe- 

 cially during the pupal period. Many pupae are thrown from the 

 cocoon to the ground by the feet of animals striking the weeds in 

 which the cocoons have been placed. Some of these dislodged pupae 

 undoubtedly perish, but unless lying directly exposed to the heat of 

 the sun or crushed by passing feet the majority of those on the 



