30 



BULLETIN 351, U. S. DEPARTMENT OF AGRICULTURE. 



Table XXII shows the time spent in the second instar by larvae at 

 Mont Alto. The orchard data are derived from the maximum daily 

 emergence and the maximum daily molts. These data show for 

 the season of 1912 a variation in the length of the instar from 16 to 

 36 days. Most of the specimens in the orchard, from July 20 to 

 August 5, spent 20 days in the instar, while in the rearing of July 22 

 two-thirds of the larvae completed the instar in 18 days. 



Table XXII. — Data showing the length of the second instar of the terrapin scale from 4 

 rearing s of larvae at Mont Alto, Pa. 



Year. 



Brood. 



Emerg- Beginning of sec- 

 ence. ond instar. 



End of second instar. 



Length 

 of the 

 instar. 



1912 



Rearing A 



Rearing B 



Rearing A — 

 Rearing B 



July 22 

 Aug. 9 

 June 24 

 June 26 



Twentieth day 



Twentieth day 



Twenty - second 

 day. 



Nineteenth day... 



First specimen, thirty-sixth day 



Maximum number, thirty-eighth day . . . 

 Last specimen, forty-ninth day 



Days. 

 16 

 18 

 29 





First specimen, thirty -sixth day 



Maximum number, thirty-eighth day. .. 

 Last specimen, fifty-sixth day 



16 

 18 

 36 



1913.... 



First specimen, thirty-fifth day 



Maximum number, thirty-ninth day 



Last, specimen, fifty-third day 



13 

 17 

 31 





First specimen, thirty-third day 



Maximum number, thirty-seventh day . . 

 Last specimen, thirty-ninth day 



14 

 18 

 20 









In 1913 the maximum daily orchard emergence was two days earlier 

 than in 1912. The first instar required 18 days as against 20 days 

 for the previous year. However, when the age at the end of the 

 second instar is considered, it appears that in both seasons the maxi- 

 mum numbers completed the instar upon the fortieth day. 



The larvae used in Table XXII were placed upon 1-year-old peach 

 trees. For the date of entering the instar is given the day upon 

 which the maximum number entered it, and the date of leaving the 

 instar is given for the first specimen, for the last specimen, and for 

 the maximum daily number. 



The table shows that the second instar may last from 13 to 36 days 

 and that the maximum number of specimens remain in it from 17 to 

 18 days; the greatest number molting upon the eighteenth day. 



Second Molt of the Female. 



The second molt of the female coincides with that of the male and 

 is little more than the casting of the skin in response to growth. 

 There is no change in the structure of the appendages or of the mouth 

 parts. 



In 1912 the second molt for a rearing of 213 females that emerged 

 July 22 extended over a period of 10 days. The maximum daily molt 

 was upon the thirty-eighth day after emergence, and 50 per cent 

 had molted by the fortieth day. A rearing of 1 00 females that emerged 

 upon August 9, 1912, made its maximum molt upon the thirty-eighth 

 day after emergence. One-half of the rearing molted upon that day. 



