THE NEW MEXICO RANGE CATERPILLAR. 87 



Few, if any, of those moths that were living when the snow came 

 survived the severe cold, and the dead moths were seen on the 

 ground by the thousand; mostly, however, males. Hence those 

 that appeared after the snow were fresh from the chrysalis. 



DEFENSIVE METHODS. 



Every moth of this species, when it emerges from the pupal case, 

 contains within its abdomen a sac of defensive fluid. This sac is 

 situated near the tip of the body and the included fluid is white or 

 milky in appearance. If the moth is touched or thrown from its 

 perch to the ground, its first instinctive movement is to throw the 

 wings back from the body and to bring the abdomen forward until its 

 extremity almost touches the face. The contents of the sac are then 

 discharged, sometimes with considerable force, by a series of im- 

 pulses that empty it entirely. If the sac has already been unloaded 

 the moth will lie as if dead for some minutes unless the heat of the 

 sun compels it to seek a cooler place. Even when nearly dead from 

 cold, the moth, when disturbed, invariably throws back the wings 

 and curls the body forward, as described. 



When the moment for flight has arrived, the moth, if previously 

 undisturbed since emergence, always discharges the fluid from the 

 sac as a preliminary act before taking wing. This habit affords a 

 method for determining with certainty whether any given moth has 

 been in the air. 



The male always discharges this fluid before mating, since he 

 invariably flies in search of his mate. The female does not always 

 rid herself of the contents of the sac at the approach of the male, but 

 seems compelled to do so before oviposition. 



It is one of the peculiar facts known of this species that it should 

 be so well equipped for defense against enemies that do not appear 

 to attack it in its present mode of existence. It may be a survival 

 of defense that was once needed and of habits that were acquired in 

 some previous phase of its life, before the species became graminivo- 

 rous. 



NATURAL ENEMIES. 

 INSECT PARASITES. 



During the month of September, 1909, large numbers of pupae of 

 Hemileuca were collected and dissected to ascertain if possible the 

 extent and success of parasitic attack. These gatherings were made 

 from somewhat widely separated parts of the infested district, and 

 probably give as fair a general view of existing conditions as could be 

 obtained. 



