10 BULLETIN 256, U. S. DEPARTMENT OF AGRICULTURE. 



@dges meeting near their tips. With feeding and growth of the nymph 

 tlse abdomen elongates without a corresponding growth of the wings, 

 with the result that the latter reach only about to the sixth abdominal 

 segment just before transformation to the adult. The prothorax 

 ©xtends slightly over the dorsum of the metathorax. The white 

 rings on the antennae, which have grown gradually fainter with each 

 sacceeding molt, are now but faintly visible. The external genitalia, 

 the ovipositor in the female and the forked, supraanal spine in the 

 male, appear to be almost as fully developed as in the adult. The 

 ttymph is about five-eighths inch long just after the molt to this instar. 



Fig. 10. — The fork-tailed katydid: Sixth-instar nymph. About three times natural size. (Original.) 

 DURATION OF INSTARS. 



The duration of instars, averaged from all our records, was as 

 follows: Instar I ranged from 10 to 35 days, with an average of 18.8 

 days; instar II ranged from 8 to 13 days, with an average of 9.7 days; 

 instar III ranged from 4 to 12 days, with an average of 7.1 days; 

 instar IV ranged from 6 to 10 days, with an average of 8.3 days; 

 instar V ranged from 3 to 15 days, with an average of 10.4 days; 

 instar VI ranged from 12 to 20 days, with an average of 14 days. 

 The complete nymphal stage required from 58 to 88 days. Nymphs 

 issuing early in the spring were slower to become adults than those 

 issuing later when the average temperatures were higher. 



After feeding for from 1 to 3 weeks the nymph ceases to eat and 

 semains sluggish for from 24 to 48 hours. The skin then splits along 



