ORCHARD INJURY BY HICKORY TIGER-MOTH. 9 



The larvae reared in 1915 passed through only 8 instars, but the 

 majority of those reared in 1916 passed through 9 instars. This 

 could not have affected greatly the time required for development, 

 however, as the few larvae which passed through only 8 stages in 

 191G required an average of 88.71 days. In 1915 the larvae were 

 reared under natural conditions in bags on a tree, whereas in 1916 

 all lots but one were reared in battery jars. The one lot of 22 larvae 

 reared on the tree in 1916 required from 85 to 92 days from egg to 

 cocoon, with an average of 87.18 days, very nearly the same as that 

 of those reared in confinement. 



No explanation is offered for the difference in time required for 

 development of larvae in the two seasons, but it should be stated 

 that the season of 1915 was excessively rainy, whereas the 1916 sea- 

 son was excessively dry. It is probable that humidity affected the 

 rate of development either directly or by its effect upon. the food 

 plant. 



The duration of the larval feeding period varies somewhat when 

 different food plants are used. The development of those reared on 

 apple was similar to that on walnut, but a little slower, and the 

 larvae passed through only 8 stages. The shortest period required 

 for development from egg to cocoon was 89 days and the longest 

 was 96 days, with an average of 92.87 days. 



Pear seemed a slightly more favorable food plant than apple. The 

 development of the larvae was more rapid, and although the majority 

 passed through only 8 stages a few passed through 9 stages. Eight- 

 een larvae which passed through 8 stages required from 87 to 91 

 days, with an average of 88.77 days; 5 larvae which passed through 

 9 stages required from 98 to 100 days, averaging 98.40 days. 



The duration of the stages of larvae reared on Japanese walnut 

 during the season of 1916 was as follows: 



First stage: Minimum 6 days, maximum 7 days, average 6.12 days; 232 

 larvae reared. 



Second stage: Minimum 4 days, maximum 7 days, average 4.78 days; 232 

 larvae reared. 



Third stage: Minimum 5 days, maximum 7 days, average 5.62 days; 232 

 larvae reared. 



Fourth stage: Minimum 6 days, maximum 7 days, average 6.02 days; 232 

 larvae reared. 



Fifth stage: Minimum 6 days, maximum 8 days, average 6.25 days; 232 

 larvae reared. 



Sixth stage: Minimum 6 days, maximum 13 days, average 8.52 days; 145 

 larvae reared. 



Seventh stage: Minimum 8 days, maximum 20 days, average 12.33 days; 145 

 larvae reared. 



Eighth stage (excluding larvae that completed their feeding period in this 

 stage) : Minimum 13 days, maximum 25 days, average 18.03 days; 138 larvae 

 reared. 



