80 
WHITE FLIES INJURIOUS TO CITRUS EN FLORIDA. 
Length of Lite Cycle. 
Data concerning the duration of the egg, larval, and pupal instars 
of the citrus white fly have already been given, but not in a form readily 
showing the relation to the complete life cycle. From some of the 
more important and complete of the life-history studies the data in 
Table XV have been arranged to illustrate the important points in 
this connection: 
Table XV. — Length of life cycle of the citrus white fly at Orlando, Fla. 
Lot No. 
Eggs de- First fly 
posited, emerged. 
Last At First flv T t fl 
emerged i emerged z££z2ZK 
in fall, in spring. anet Seo. 
Xo. 1. 
No. 2.. 
No. 3.. 
No. 4.. 
No. 5.. 
No. 6.. 
No. 7.. 
No. 8.. 
No. 9.. 
No. 10. 
No. 11. 
No. 12. 
No. 13. 
No. 14. 
No. 15. 
Feb. 23 
Mar. 3 
Aor. 3 
Apr. 20 
June 16 
Julv 17 
..do 
Julv 19 
July 26 
Aug. 1 
Aug. 3 
Aug. 8 
Aug. 9 
Sept. IS 
Sept. 21 
Apr. 30 
May 9 
May 30 
June 7 
Julv 30 
Aug. 27 
Sept. 4 
Sept. 2 
Sept. 6 
Sept. 19 
Sept. 25 
Sept. 19 
Mar. 30 
Mar. 16 
Mar. 12 
Sept. 10 
SeDt. 17 
Sent. 21 
Sept. 20 
Sept. 26 
..do 
Sept. 27 



Mar. 
Mar. 
..do. 
Mar. 
Mar. 
Mar. 
Mar. 18 
16 Apr. 16 
17 May 4 
... May 1 
Mar. 
Mar. 
Mar. 
May 10 
Apr. 6 
Apr. 15 
May 12 
Apr. 28 
May 10 
Lot No. 
Least 
Largest 
Per cent 
Per cent 
number of 
number of 
winter- 
davs for 
davs for 
before 
winter. 
ing over 
develop- 
develop- 
to emerge 
ment. 
ment. 
m spring. 
67 
67 
57 
100.0 
100.0 
100.0 



48 
333 
44 
41 
273 
56.9 
43.1 
49 
291 
30.8 
69.2 
45 
286 
12.7 
S7.3 
42 
2\S 
29.8 
70.2 
49 
248 
5.5 
94.5 
53 
255 
3.6 
96.4 
42 
2.7 
97.3 
223 
276 

100.0 
179 
222 

100.0 
172 
231 

100.0 
Smallest 
number 
degrees 
effective 
tempera- 
ture for 
develop- 
ment. 
Degrees 
accumu- 
lating 
before 
spring 
emer- 
gence. 
Degrees 
accumu- 
lating 
before 
last fly 
emerged. 
No. 1 . 
No. 2. 
No. 3. 
No. 4. 
No. 5. 
No. 6. 
No. 7. 
No. 8. 
No. 9. 
No. 10 
No. 11 
No. 12 
No. 13 
No. 14 
No. 15 
From this table it will be seen that the period of development for 
individuals hatching from eggs laid upon the same leaf within a few 
hours of each other is subject to an astonishing variation, ranging 
from 41 to 333 days. Tins variation is absolutely independent of 
both temperature and humidity influences. It will be noted that 
the sums of effective temperatures required for the minimum dura- 
tion of immature stages for individuals developing from eggs de- 
posited between February 23 and August 8 vary from 1.641° to 
2.153°, with an average of 1,846°, which may be regarded as very 
nearly the normal for minimum development up to the time when 
