76 CEREAL AND FOEAGE INSECTS. 



halves of the body thus brought in contact, repeating this many 

 times as if much pleasure was derived from the singular action. 



LENGTH OF LARVAL STAGES. 



Repeated attempts were made during the summer of 1909 to rear 

 Hemileuca in confinement and secure data as to the length of the 

 various instars, five in number. Without exception, these efforts 

 proved failures, and for a number of reasons, some of which may be 

 mentioned here. 



As has been related elsewhere, the very young larvae are almost con- 

 stantly on the move, and any interference with their native liberty 

 is resented. Within the limits of such cages as could be devised from 

 scanty materials, these peripatetic caterpillars always became very 

 much dissatisfied, and, after exploring all the interior repeatedly, 

 would pay little or no attention to the food provided, grow listless, 

 and ultimately starve to death. 



The older forms were found to be extremely particular about their 

 food, and they usually rejected such as was furnished them, even 

 though this was the best that could be procured. When allowed to 

 choose their own food under movable cages placed on the ground, they 

 sulked, ate but little, and, where in a few cases they finally molted, the 

 development was so abnormally slow that the record of the facts was 

 worthless. 



It was learned by observation that these caterpillars, in their 

 native state, dislike exceedingly, and generally refuse to eat, grass 

 over which their mates have left the usual fine trail of silk, although 

 later this same trodden grass seems to become palatable. This 

 reason for declining to feed was perhaps one of the main obstacles to 

 success when attempting to rear these insects in confinement. 



Observations made in the open appear to show that the first three 

 instars are passed in rapid succession, each one lasting less than two 

 weeks. The fourth instar is longer, while the fifth is indefinitely 

 long, averaging at least four weeks. It is believed that these periods, 

 as given, are approximately correct. 



IRRITATING EFFECTS OF LARVAL SPINES. 



The spines with which the larvae are clothed are quite annoying and 

 irritating, giving an effect, when touched, much like that produced 

 by the urticating cells of the nettle. This irritation often lasts for 

 an hour or two, especially when the thin skin of the arm or wrist is 

 wounded. The spot puffs up almost at once, turns white, and when 

 the swelling subsides, a brown point remains for days or weeks. 

 Occasionally even' the tough skin of the finger tips proves vulnerable, 

 and a puncture there is generally very painful. 



