80 WHITE FLIES INJURIOUS TO CITRUS IN FLORIDA. 
LenetH oF Lire 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: 
TaBLeE XV.—Length of life cycle of the citrus white fly at Orlando, Fla. 

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Nees Last fly | First fly 
Eggs de- First fly i ce | Last fly - 
Lot No. posited. | emerged. ae eee emerged. 
: s g. 
INO? Wit occ Aske eae Ae Se Ee FE ee eee eee Feb. 23°) Apr: 30 2.2.22. -25|-0-5--ce=s|eeeeeeenees 
INOS2! 22 eee aaa Be 95 Sey A ee Oe oe ae Mar: 3)| May \9").:s20 2505. | ee =o sit cs Se ae Sees 
INOS 8 oe ee eae re eee et eC is tee ere ieee toe Apric 3 )| May 30! | 5.0 52] se cake ee See 
INOZ4 soo oon Soon Seen seen cen soe ee eee ee eer e ease PNG Oy 4!) jab V (See ee eens esos = 55s Mar. 18 
INO: Dee ee eee oe re een eee ot cheers June 16! | Iuky 30) |e2<- 222 -25|2- 22 -- see lee 
INO Gos < 525 oc Sule cece pene a See amciae saclay July 17} Aug. 27 | Sept.10 | Mar. 16] Apr. 16 
Sept. 4] Sept.17| Mar. 17] May 4 
Sept. -2)|Septa2l|Pe-dosss- May 1 
Sept. 6 | Sept. 20] Mar. 18| May 10 
Sept. 19 | Sept. 26 | Mar. 24| Apr. 6 









So lime Vue) jaacOOssee- Mar. 23} Apr. 15 
Si) peptr 9) | SeCDis at «|S eelee 
male Aug. 9] Mar. 30 0| Mar. 20) May 12 
INO S14 oo. Saseese 256eee Se es Re a cea ete Sept. 18 | Mar. 16 0| Mar. 16] Apr. 28 
IN ONLD oe coe ee newk ciseaas ee icie das ca oaen wn tececeee eee Sept. 21 | Mar. 12 0| Mar. 12| May 10 
Smallest 
Degrees ae 
Least | Largest | p , | Percent eae accumu- Desrecs 
number of/number of, + ° woe winter- fe hee lating Tet ake 
Lot No. days for | days for ppc ing over he cS UN before he ae 
develop- | develop- | © tee to emerge i fete spring eck fi 
ment. menty |: #00 in spring.) Woe aoo emer- bath: 
develop-| cance emerged. 
ment. : : 
Lyf ery pc 100. 0 0 ty (. 538 ee oe | sca @ tee 
iA | Pees Ses ae 100. 0 0 1, 885) ||. 2222.32. | eee 
LY | ee ee 100. 0 0 1888 ||. eet Soe ee eee 
48 2h jel eee eect | 12" |e eae ee jo ace oeeeae 
Ce ee ee see ee oe tenes nates ce L720. |p asco ee ees < = 
41 273 56.9 43.1 1, 641 6, 6382 7,619 
4g 291 30.8 69.2 , 66 
45 286 12.7 87.3 
42 288 29.8 70. 2 
49 248 555) 94.5 
53 255 3.6 96. 4 
(PAD) ee ee eS 2.7 97.3 
223 276 0 100. 0 
179 222 0 100. 0 
172 231 0 100. 0 











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. This 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 
