THE BLACK FLY OF CITRUS. 
43 
the monthly meteorological reports of the section of Meteorology 
and Hydrography of the Panama Canal, the observations being made 
at Balboa Heights. 
Table VII.— Weather report for June, 1918, to May, 1919, inclusive, at Balboa Heights. 
Temperature. 
Wind. 
Mean 
rela- 
tive 
humid- 
ity. 
Rain. 
Month. 
Maxi- 
mum. 
Mini- 
mum. 
Mean. 
Pre- 
vail- 
ing 
direc- 
tion. 
Hourly 
aver- 
age 
move- 
ment. 
Maximum 
velocity and 
direction. 
Per 
cent. 
Rainy 
days. 
Maxi- 
mum 
in 
one 
day. 
Total 
for 
month. 
°F. 
91 
°F. 
72 
73 
72 
72 
71 
70 
71 
70 
70 
67 
72 
73 
°F. 
80.2 
81.6 
80.8 
80.8 
79.8 
80.2 
81.0 
79.8 
81.4 
80.8 
81.6 
81.2 
N. 
NW. 
NW. 
NW. 
NW. 
NW. 
N. 
N. 
N. 
N. 
NW. 
NW. 
Miles. 
6.6 
7.6 
7.7 
5.6 
7.2 
6.3 
9.4 
11.5 
11.7 
13.7 
9.1 
6.5 
Miles per hr. 
23 N 
88.4 
88.6 
89.0 
89.6 
89.8 
90.1 
85.6 
77.8 
74.4 
72.9 
80.1 
86.0 
17 
13 
14 
13 
19 
16 
5 
7 


15 
23 
Inches. 
1.58 
1.75 
1.07 
2.35 
2.20 
2.46 
.24 
.12 
Trace. 
Trace. 
1.42 
1.29 
Inches. 
5.20 
5.13 
3.84 
7.03 
9.16 
9.61 
.55 
.28 
Trace. 
Trace. 
6.43 
5.21 
1918. 
June. 
91 
91 
91 
91 
92 
91 
90 
94 
92 
93 
92 
28 NW 
36 NW 
27 NW 
28 NW 
28 NW 
28 NW 
32 NW 
32 NW 
36 NW 
31 NW 
30S 
July. 
August. 
September. 
October. 
November. 
December. 
1919. 
January. 
February. 
March. 
April. 
May. 
With such a radical change in the rainfall it is no wonder that the 
development of woglumi is decidedly checked. Attention has already 
been called to this under the heading of "Injury/' page 18. Out of 
12 spirals consisting of 421 eggs on trees exposed to a free play of the 
wind and started between December 8, 1918, and March 4, 1919, and 
observed by Mr. Molino, only 245 hatched, 52 reached the first larval 
instar, 15 the second larval instar, 14 the pupal stage, and 9 the adult 
stage. Hence, it is no wonder that an incipient infestation observed 
in Las Sabanas in January, 1919, died out by April of that year. 
Furthermore, the citrus trees when not watered during the dry 
season make little or no growth, and such growth as was uninfested 
before the beginning of the dry season in places exposed to the wind 
remained so even on trees that were watered. Such young growth 
as was made on watered trees also remained practically free. 
Likewise the abundance of adults during the dry season is an indi- 
cation of the seasonal history. During the rainy season there usually 
is a considerable number of adults present on the young or on the 
terminal growth of an infested tree. At the beginning of the dry 
season in December, this abundance of adults shows a decided falling 
off, few or no adults being present on the terminal growth except for 
from four to five days following a shower. After a shower consider- 
able numbers would be present, but they would dwindle down to 
none within three to four days. This was shown on three different 
