64 
Table XVIII. — Duration of larral instars. 
;tage 
I. 
Period of growth. 
Stage Stage 
11. III. 
Stage Stage Stage ' ^ . , is 
IV. V. VI. j ^^^^^- ^Si 
g-^ 
Corn stems 
do 
do 
Rosebuds 
Corn silk 
do 
7 I do 
8 Cotton 
9 ' do 
....do 
Tobacco ! 
Cotton I 
....do 
....do 
Miscellaneous . . 
Cotton 
Araarantus 
Tobacco 
Cowpeas i 
Cotton 
Tobacco 
Tomatoes | 
Cotton I 
..-.do 
...-do i 
....do 
Cowpeas 
Cotton 
Apr. 1-Mav9 
Apr. 10-Mav9... 
Apr.l9-Mayl6.. 
May 1.5-June 3. . 
June 29-Julv 17. 
Julv9-Julv'25.. 
Julvl9-Aug.2 .. 
Julv 19-Aug. 3 - . 
Julv29-Aug.l3. 
July 30-Aug. 16 . 
Aug. 4-Aug. 19 - 
Aug. 7-Aug. 22 . , 
Aug. 8-Aug. 24 - , 
Aug. 8-Aug. 23 . 
Aug.8-Sept. 6.. 
Aug.20-Sept.8. 
do 
Aug. 20-Sept. 9 . 
Aug. 20-Sept. 1 . 
Aug. 31-Sept. 18 
Aug.31-Sept.l6 
Aug. 31-Sept. 20 
Aug. 31-Sept. 17 , 
Sept.8-Sept.25-, 
Sept.l6-Oct.5.. 
Sept.20-Oct. 20. 
Sept.28-Oct.21. 
Oct. 13-Dec. 20 . . 
Average . 
11 
2 
2 
2 
3 ! 2 
15 2 
4 4 
19 
21 i(«) 
7 6 
5 5 
23 3 
2 i 2 
18 
23 
S 
13 
20 ' 
4 
2 
14 
21 
2 
15 
18 
17 2 
22 3 23 5 1 
37 ; 12 
24 : 6 
27 : 11 
16 , 13 
16 22 
14 21 
14 17 
26 10 
17 23 
19 17 
20 15 
11 j 22 
20 i 23 
21 
6 
18 
16 
17 

19 
1 
29 
1 
21 
19 
70 
3 
°F. 
810 
440 
677 
871 
668 
656 
532 
657 
682 
632 
547 
566 
525 
520 
1,033 
681 
737 
802 
478 
735 
656 
702 
646 
429 
687 
960 
637 
c-643 
a Omitted. 
b Not recorded. 
In this average Nos. 15 and 28 are omitted. 
In the last column are given the sums of effective temperature 
(above 43^) to which the larvas were subjected. While the range ^' 
(429^-871°) is great, an average of 617^ does not fall far from most of 
the records. 
The following table shows the average length of the different instars 
for larvae feeding on corn and cotton: 
Table XIX. — Average length of larval instars for larva; fed on corn and cotton. 
Instar. 
Days? 
1 
Hours. 
I . 
II . 
III. 
IV . 
V . 
VI . 
3 
3 
3 
I 
13 
6 
17 

19 
11 
Total 
20 
18 
GROWTH DITRIXG THE LARVAL IXSTARS. 
The comparative rate of growth during the respective larval instars 
is of interest as indicating the periods of most vigorous feeding, and, 
a Only rearings on corn and cotton are here considered. 
