THE NEW MEXICO RANGE CATERPILLAR. 83 



where, p. 87), bringing her body forward and up as she does so. The 

 male will at first wriggle and rock his body, rotating his head in a very 

 peculiar fashion, intended perhaps to inspire terror in the intruder. 

 If the annoyance continues or becomes more severe, he curls the 

 body forward and ejects the milky fluid with some force. When 

 this action fails to remove the disturber, the moths often release their 

 hold, fall to the earth, and "play possum." 



They are with great difficulty induced to walk to some other part 

 of the plant on which they are resting. 



About 4.30 in the afternoon the male moths begin to stir. The 

 antennse wave slightly and presently the wings are spread little by 

 little until they lie out flat. Soon the wings are in rapid vibration, 

 for a few seconds at a time, after which they may be partly folded and 

 the moths become quiet again. But very soon the insect grows 

 wide awake, takes a few jerky steps, hesitates again, then runs to 

 the top of the stem on which he has been resting, and launches him- 

 self for his crepuscular flight. 



The female is much more deliberate in her movements and rarely 

 takes to wing before 5 p. m. She indulges in the same halting pre- 

 liminaries as the male, but when she finally flies she rises gradually, 

 often to a height of 30 or 40 feet, appears to get her bearings, then 

 sails off in a straight line from which she seldom or never deviates. 



For some unexplained reason many of the females fail to mate where 

 they emerge, and these virgin females are the ones that fly to distant 

 parts of the range, carrying their eggs, which are probably fertilized 

 by roving males, and are deposited in hitherto uninfested regions. 

 It is possibly those individuals that emerge from the pupae earliest 

 in the morning that fly in this manner, while the ones emerging 

 later remain on the natal plant until found by the male. 



October 16, 1908, a number of females, perhaps 20, were moved, 

 late in the afternoon, to one plant for better observation. Between 

 5 p. m. and dusk every member of this colony rose in the air and 

 disappeared, not one having attracted a mate, although males were 

 numerous all about. The same experiment was tried several times 

 during both 1908 and 1909, with the same result, while mated couples 

 (see fig. 46) were everywhere clinging to the weeds. 



When the male, hovering in the air, discovers a virgin female he 

 drops to the ground or alights below her on the stem and runs up, 

 his wings in rapid vibration, until she is reached, when copulation 

 takes place immediately. Owing to the predominance in number 

 of the males there is often much strife over the possession of a mate, 

 and frequently six or more males are seen fluttering about a single 

 female. 



On two different occasions during the progress of these investiga- 

 tions a male moth was found mated with a spent female which had 



