THE NEW MEXICO RANGE CATERPILLAR. 73 



THE LARV^. 



HABITS OF THE YOUNG LARVAE. 



The young larvae, when they emerge from the egg, are a dull brick- 

 red. This color changes in a few hours, becoming very dark, nearly 

 black. They are quite sluggish at first, but are somewhat positively 

 phototropic and show a tendency to colonize on the side of the 

 cylindrical egg cluster that is most exposed to the light. 



Their emergence is gradual and usually a day or two is required 

 for all the inmates of a single cluster to appear. The newly emerged 

 larvae are conspicuous red individuals among a mass of darkened 

 forms. As their numbers increase they give to the immediate land- 

 scape a peculiar appearance, for they show as little black balls here 

 and there on grass sods and weed stems. Their favorite exercise is 

 to raise the front half of the body free and wave it to and fro a number 

 of times, somewhat rapidly. 



When kept in confinement they often spin a carpet of silk over the 

 surface of the eggshells, but this is seldom seen out of doors. 



For several days after hatching the young caterpillars remain 

 massed about the remains of the eggs (PI. IV, fig. 2), feeding occa- 

 sionally on the empty shells. They are continually in slight motion, 

 their black, shiny bodies glistening in the sunlight as they constantly 

 change places. The group gradually breaks up as the earlier-hatched 

 ones string away from the parent colony in processions of 20, 30, or 

 40. These move in single, double, and triple file, the inequalities of 

 the ground compelling constant changes in formation. 



This processional habit, better known and more exhaustively 

 studied in the well-known and widely distributed species Hemileuca 

 maia Dru., is very amusing and is persisted in until the third larval 

 instar, after which the individuals appear much annoyed at the near 

 approach of a neighbor, large or small. The processions, as they 

 move about on the mesa, seldom go in straight lines, but are guided 

 apparently by the caprice of the one that happens to be in the lead. 

 There is no rest for the leader, for if it happens to pause for a moment, 

 the movement from the rear compels progress, and off the line goes 

 again, toiling across the surface. Often the leader ascends a grass 

 blade, reaching the top, swings about, catches the nearest blade if 

 within reach, if not, goes down the other side while the procession is 

 still passing up. These parties often subdivide, and if the}^ come 

 upon another lot during their rambles the two processions may 

 coalesce. Removal of the temporary leader seems to produce no 

 perceptible effect on their movements, and in no case does there seem 

 to be any definite goal in sight. The column will often "ball up," 

 remain in a black mass, sometimes an inch or more in diameter, on a 



