62 WHITE FLIES INJURIOUS TO CITRUS IN FLORIDA. 
DURATION OF STAGES 
LARVAL INSTARS. 
Data upon the duration of the larval instars nave been secured by 
daily observations of over 300 specimens marked as soon as the 
young larve 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 larve 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. 
TaBLeE IX.—Duration of larval instars of the citrus white fly. 






















| 
Number of | ; Number of 
days in— Sum of days in— Sum of 
Speci- effec- Il speci- : effec- 
men | Period of growth. nye men | Period of growth. tive 
8 ; tem- tem- 
| No. In- In- in- pera- No. In- In- Tn- pera- 
star | star} star Fmree star | star | star Hires 
ls 2. 3. 1 2 3. 
1 | Mar. 22-Apr. 26...] 13 10 12 1,044 33 | Oct. 3-Oct. 27...- 7 5 12 736 
| el Ne ee G02 8222 eee 34 | Oct. 3-Oct. 30.... 5 8 14 811 
Oe eee Govecc sess 35 | Oct. 3-Nov. 11...- if 15 17 |. a5102 
| anes (6 Ke ass at 36 | Oct. 3-Oct. 29.... 7 8 11 792 
Silt a Oi 23:-ceeees 37 | Oct. 3—Dec. 4..... rai 14 17 | 1,644 
Bilsesse GO. wencnceee 9 38 et Buer Al 12 i 13 922 
(oe Gove ween cee 9 39 | Oct. 3-Nov. 1..... 8 8 13 843 
8 | June 26-J uly 18.22! 2S 7 898 40 Oct. 3-Nov Dea 8 i 15 | 868 
9 | June26-July 19...) 8 5 10 938 41 | Oct. 3-Nov. 3.-...- 9 15 894 
10 | June 26—-July 16...) 8 5 #f 813 423 ace dove c.eoeseee 11 i 13 894 
11 | June 26-July 18...) 7 6 9 898 43 | Oct. 3-Nov. 1..-<- 8 8 13 843 
12 | June 26-July 20... 8 4 12 978 44 | Oct. 3-Nov. 10..-- 7 4 17 | 1,060 
13 | June 26-July 18... 8 5 9 898 45.| Oct. 3-Oct. 31.... 8 8 12 828 
14 | June 26-July 29... 8 5 ZO") Vireo. 46 | Oct. eevs ; cae 4 7 2 ; ce 
15 | June 26-July 18... 8 5 9 898 47 | Oct. 3-Nov. 8....- 7 y , O12 
16 Tare 26 July 212 8 5 12 1,015 AS i ese do. s.eéeceten 7 10 19 | 1,012 
iH June ae 1836 28 3 9 oe a, Bee pe 2 ace 7 ; = oe 
8 | June 26-July 16... 7 8 813 et. OVvesleee i 
19 | June 26-July18...| 8 5 9 898 || 51] Oct. 5—-Nov. 7... tiga gikyy 11 932 
20 | June27-July19...| 7 5 10 902 52 | Oct. 5—Oct. 31....| 5 8 13 768 
21 | June27-July 20...| 8 5 10 ee 53 ore ee S22 -b| 8 8 2 ate 
D2 Ne ee ol-este ae of 8 8 642 |) 54 ct. 5—-Nov. 5..... 9 8 4 
23 | June 27-July 16... i, 5 7 777 55 | Oct. Om Tessas 8 : “4 S 
24 | June 28-July 21...) 6 6 11 938 || - 56 | Oct. 5B—-Nov. 3....- 9 
25 | June 28-July 28... us 9 14 1, 220 57 | Oct. 5-Nov. 5..... 8 9 14 883. 
26 | June28-July18...] 6 5 9 821 58 | Oct. 5-Nov. 1...-.- 10 Siege 783 
27 | June 29-July 27...) 5 4 19} 1,141 59 | Oct. 5—Nov. 19....| 11] 34 | died.|........ 
28 | July 28—-Aug. 18... 5 4 12 ; 866 60 | Oct. 5-Oct. 31... . 6 8 13 767 
29 | Sept. 28-Nov.14..} 7] 106 30 365 
30 Sept . 30-Oct. 25... 7 6 12 780 | Aver- Tune 26-Au 9\r ; 5 
; . : se if 3 2 g.18...| 7.2 | 5.4 | 10.5 | 945.7 
bavi magica mad Ben ee pc SP S| {Sept 28-Dec. 4.111178 8.3 | 14.3 | 903.4 
| | ) 


1 Does not include No. 37. 2 Does not include No. 59. 
