THE NEW MEXICO RANGE CATERPILLAR 71 



LOCATION' OF THE EGO-MASSES. 



The egg-masses, the characteristic appearance of which is well 

 shown in figure 32, and in Plate III, figure 3, are exceedingly numer- 

 ous on many parts of the range. They are frequently placed in close 

 proximity to each other, and as many as six and eight clusters have 

 been counted on the stems of a single small sod of grass. Numerous 

 instances have been observed where a single stem has furnished sup- 

 port for three or four egg-masses, each female as she arrives con- 

 tinuing the cylinder previously begun, until the aggregate length of 

 the masses is sometimes 2 and even 3 inches. 



It is a curious fact that few of the eggs are placed upon the food 

 plants of the young caterpillars, but they are placed upon any plant 

 that affords the necessary support for the egg cylinder, regardless of 

 the needs of the larvae. 



HATCHING. 



(Plate IV, fig. 2.) 



All the eggs in a single cluster are opened by the larvae within at 

 about the same time. The first sign of internal activity is a very 

 small hole, like a minute pin prick, in the vicinity of the micropyle. 

 This opening is made by a thrust of the mandible from within and 

 is enlarged very deliberately, the operation often requiring two or 

 three days. The dense structure of the shell offers much resistance 

 to the tiny jaws, so that a passage large enough for exit is bitten 

 through with difficulty. An entire day will often pass without any 

 perceptible gain in the opening, but eventually it is completed, for 

 very few larvae die in the shell. 



That the thick shell of the egg is highly protective for the 

 unhatched larva? is shown by the fact that clusters of eggs dipped 

 in alcohol, as well as others kept for several days in fresh cyanide 

 bottles, all hatched, having evidently been uninjured by this drastic 

 treatment. 



The imprisoned larvae seem very timid and will rarely make a 

 move either to enlarge the opening or to escape from the egg while 

 under observation. 



When the aperture in the egg has been enlarged until it corresponds 

 nearly to the size of the face plate, which is the only rigid and unelastic 

 part of the larva, the head is withdrawn from its position before the 

 opening, the caudal end is thrust out, and little by little the tiny 

 prisoner makes its escape. Not infrequently the face plate fits the 

 doorway so snugly that a protracted struggle is necessary before the 

 head can be extricated. 



