28 



BULLETIN 351, U. S. DEPARTMENT OP AGRICULTURE. 



age age for this molt in 1912 was 20 days, but this period is longer 

 than in favorable years. During the favorable season of 1913 a few 

 specimens from the rearing of July 1 made this molt on the sixteenth 

 day, but the largest daily molts were from the eighteenth to the 

 twenty-second day, with the maximum molt upon the eighteenth day. 

 It is, however, very frequently delayed. Table XX gives details of 

 the first molt as shown by three rearings in 1913 and by data ob- 

 tained in orchards in 1912. It will be noticed that in all cases molt- 

 ing started either upon the sixteenth or seventeenth day and that it 

 terminated in all cases by the twenty-sixth day. The 1913 rearings 

 all had favorable weather and would undoubtedly all have given 

 their maximum daily molts upon the eighteenth day had it not been 

 for a local storm on that date which retarded the natural emergence 

 for the rearings of June 24 and June 26. 



Table XX. — Details of the first molt of the terrapin scale from 3 rearings in 1913 and 



from orchard data of 1912. 



Date larvae 

 emerged. 



Age at 

 start- 

 ing of 

 first 

 molt. 



Per cent molted at various days specified. 



Age at 

 maxi- 

 mum 

 daily 

 molt. 



17th. 



18th. 



19th. 



20th. 



21st. 



22d. 



26th. 



July 1,1913... 

 June 24, 1913. 

 June 26, 1913. 

 Orchard lar- 

 vae 1912.... 



Days. 

 16 

 16 



16 



17 



20 

 2 

 5 



52 



80 







100 

 85 

 100 



"""ioo" 



Days. 

 18 

 22 

 19 



20 





40 



91 



20 

 C 1 ) 



60 



90 











i Blanks represent days upon which no data were taken. It was impossible to determine, under orchard 

 conditions, the percentage of the total infestation that molted at definite ages. 



LEAF-ATTACHED LARVAE, SECOND INSTAR. 



The second instar lasts in favorable weather for 18 days and 

 usually extends from the eighteenth to the thirty-sixth day. In the 

 orchards about Mont Alto specimens can be taken in this instar at 

 almost any time after the middle of July. The instar is at its maxi- 

 mum from July 20 to August 5. This stage of development is char- 

 acterized by sexual differentiation, which begins very early in the 

 instar. The female larvse continue to widen and tend to become 

 circular in outline, while the males lengthen and tend to become oval. 



The male secretes during this instar the characteristic puparium. 

 This is a waxy scale which forms over the dorsal surface. It is roof- 

 like and is held in place by elastic strands which extend from points 

 upon its edges to the surface of the leaf. (PI. II, a, e, p. 52.) It 

 can be recognized as early as the seventh day, but it does not reach 

 its full development until the next to the last day of the instar, at 

 which time growth ceases and the larva shrinks, preparatory to 

 making the second molt. 



