62 
WHITE FLIES INJURIOUS TO CITRUS IX FLORIDA. 
DURATION OF STAGES 
LARVAL INS TARS. 
Data upon the duration of the larval instars nave been secured by 
daily observations of over 300 specimens marked as soon as the 
young larvae had settled, supplemented by frequent counts of several 
thousand specimens in various life-history cages. 
From these records those included in Table IX have been chosen 
as representative. A study of these will give a very accurate knowl- 
edge of this subject, and will impress upon one the considerable 
variation in the duration of the several instars of larvae hatching 
at the same time, feeding upon the same leaf, and consequently sub- 
ject to the same weather conditions. The data also emphasize the 
retarding effect of cool spring and fall weather upon the length of 
larval life, although this has not been found to be as great as many 
have thought. The period of larval growth ranges from an average 
of 23 days during the warmest months to an average of 30 days 
during the cooler months. 
Table IX. — Duration of larval instars of the citrus white fly. 
Speci- 
men 
No. 
Period of growth. 
Number of 
days in — 
Sum of 
effec- 
tive 
tem- 
pera- 
tures. 
Speci- 
men 
No. 
Period of growth. 
Number of 
days in— 
Sum of 
effec- 
tive 
tem- 
pera- 
tures. 
In- 
star 
1. 
In- 
star 
2. 
In- 
star 
3. 
In- 
star 
1. 
In- 
star 
2. 
In- 
star 
3. 
1 
2 
3 
4 
5 
6 
7 
8 
9 
10 
11 
12 
13 
14 
15 
16 
17 
18 
19 
20 
21 
22 
23 
24 
25 
26 
27 
28 
29 
30 
31 
32 
Mar.22-Apr.26... 
do 
13 
11 
9 
10 
11 
9 
9 
8 
8 
8 
7 
8 
8 
8 
8 
8 
8 
7 
8 
8 
7 
7 
6 
7 
6 
5 
5 
7 
7 
6 
7 
10 
12 1.044 
33 
34 
35 
36 
37 
38 
39 
40 
41 
42 
43 
44 
45 
46 
47 
48 
49 
50 
51 
52 
53 
54 
55 
56 
57 
5S 
59 
60 
Aver- 
age.. 
Oct. 3-Oct. 27 
Oct, 3-Oct. 30 
Oct, 3-Nov. 11 
Oct. 3-Oct. 29 
Oct. 3-Dec. 4 
Oct, 3-Nov. 4..... 
Oct. 3-Nov. 1 
Oct. 3-Nov. 2 
Oct. 3-Nov. 3 
do 
7 
5 
7 
7 
31 
12 
8 
8 
9 
11 
8 
7 
8 
10 
7 
7 
7 
7 
5 
5 
8 
9 
8 
9 
8 
10 
11 
6 
5 
8 
15 
8 
14 
8 
7 
7 
7 
8 
4 
8 
7 
7 
10 
9 
7 
17 
8 
8 
8 
6 
8 
9 
6 
34 
8 
12 
14 
17 
11 
17 
13 
13 
15 
15 
13 
13 
17 
12 
15 
22 
19 
14 
13 
11 
13 
18 
14 
13 
12 
14 
11 
died. 
13 
736 
811 
1,102 
792 
1,644 
922 
843 
868 
894 
894 
843 
1,060 
828 
922 
1.012 
1,012 
868 
783 
932 
768 
952 
883 
783 
834 
883 
783 
"*767*' 
do 
do 
...do 
| 
do 
1 
do 
June 26- July 18... 
June 26-July 19... 
June 26- July 16... 
June 26-July 18... 
June 26- Julv 20... 
June 26- July 18... 
June 26-July 29... 
June 26- July 18... 
June 26- July 21... 
June 26- July 18... 
June 26- July 16... 
June 26- July 18... 
June 27- July 19... 
June 27- July 20... 
do 
7 
5 
5 
6 
4 
5 
5 
5 
5 
5 
5 
5 
5 
5 
8 
5 
6 
9 
5 
4 
4 
10 
6 
7 
9 

7 
10 
7 
9 
12 
9 
20 
9 
12 
9 
8 
9 
10 
10 
8 
7 
11 
14 
9 
19 
12 
30 
12 
10 
7 
898 
938 
813 
898 
978 
898 
1,365 
898 
1,015 
898 
813 
898 
902 
942 
942 
777 
938 
1,220 
821 
1,141 
866 
1,365 
780 
727 
635 
Oct. 3-Nov. 1 
Oct. 3-Nov. 10.... 
Oct. 3-Oct. 31 
Oct. 3-Nov. 4 
Oct. 3-Nov. 8 
do 
Oct. 3-Nov. 2 
Oct. 5-Nov. 1 
Oct. 5-Nov. 7 
Oct. 5-Oct. 31 
Oct. 5-Nov. 8 
Oct. 5-Nov. 5 
Oct. 5-Nov. 1 
Oct. 5-Nov. 3 
Oct, 5-Nov. 5 
Oct. 5-Nov. 1 
Oct. 5-Nov. 19.... 
Oct. 5-Oct. 31 
JJune26-Aug.l8... 
\Sept. 28-Dec. 4... 
June 27- Julv 16... 
June28-Julv21... 
June 28- Julv 28... 
June 28- Julv 18... 
June29-Julv27... 
Julv28-Aug.l8... 
Sept.28-Nov. 14.. 
Sept.30-Oct.25... 
Sept.30-Oct.23... 
Oct.l-Oct.21 
7.2 
17.8 
5.4 
2 8.3 
10.5 
14.3 
945.7 
903.4 
i Does not include No. 37. 
Does not include No. 59. 
