THE NEW MEXICO RANGE CATERPILLAR. 



85 



males that gathers about one's head frequently becomes a nuisance 

 by reason of the persistence of the moths composing it. 



Under certain conditions the males, when disturbed in their search, 

 will rise high in the air and fly away in a straight course, horizontally, 

 exactly as do the females. 



The flight of the females is very different from that of the males. 

 From the moment of launching from the weed-top into the air the 

 female seems to steer a definite course, and seldom varies at all from 

 the direction chosen at the start. This course is usually with, or at a 

 slight angle with, the wind, although some evenings they will fly 

 continually directly across the breeze or even against it. The flight 

 is all in one given direction as a rule on any one evening. 



Fig. 47.— Diagram illustrating life cycle of Hemileuca olivix. (Original.) 



How far the females travel, carrying their eggs, is largely a matter 

 of conjecture, but as they fly at the rate of 8 to 10 miles an hour, with 

 a somewhat heavy but strong muscular action, there seems good 

 reason to believe that they traverse long distances before they alight. 



The fluttering myriads of moths that appeared during October, 

 1909, were present over very wide areas in almost incredible numbers, 

 day after day. Taking into account the fact that the life of the 

 individual moth rarely if ever exceeds three days, the successive multi- 

 tudes, practically undisturbed by enemies, intent solely in providing 

 for the further spread and increase of the species, constitute a menace 

 to the entire range country of the Southwest that needs only to be 

 seen to be appreciated. 



99370°— Bull. 85—11 7 



