LOSSES PROM will II. ll.Y PREVENTED. 59 
ECONOMY OF TREATMENT BY FUMIGATION. 
LOSSES PREVEN III'. 
bite Hy (figs. 8, 9) Is 
grove, much benefit \\ ill 
Fig. 8.— White fly (Aleyrodes citri) : a, Orange leaf, show- 
ing infestation on under surface, natural size; b, egg; 
c, same, with young insect emerging: <l. larval Insecl : 
e, foot of same; /, larval antenna; g, scale like pupa; 
h, pupa about to disclose adult insect : i, insecl escap- 
ing from pupal shell; j, leg of newly emerged insect, 
not yet straightened and hardened. All figures ex- 
cept a greatly enlarged (rcengravcd from Rilej and 
Howard). 
Losses from tin irhih ////. When once tin 
reduced to an inconsiderable quantity in 
result from careful inspec- 
tions and fumigations of sin- 
gle trees, or groups of trees, 
from time to time wherever 
the insects are found to be 
multiplying. This will greatly 
delay the t ime when the mul- 
tiplication o( the insects shall 
have made a general treat- 
ment again necessary. This 
practice is followed in Califor- 
nia in the control of various 
scales. In wel 1-cared-for 
groves, or where the county 
horticultural commissioners 
require it. scales are kept in 
complete subjection by fumi- 
gation and the appearance of 
only a few live scales on a tree is considered a reason for fumigating 
it and perhaps, also, surrounding trees as well, although these may 
appear entirely free from the pest. The best results from fumiga- 
tion are obtained when once the 
various pests are brought under 
control by continuing the prac- 
tice as a preventive rather than 
as a remedy. In other words, 
when conditions for successful 
fumigation for the white fly are 
favorable or after they have 
been made so/' fumigation can 
be practiced with such success 
that all damage from the white 
fly will be obviated. When once 
the practice has been adopted a 
grov» er should not wait until the 
foliage 1 is blackened by the in- 
sects before Fumigating the second time. It would be far more eco- 
nomical to fumigate regularly once in two years, and prevent all 
blackening of the foliage, than to fumigate once and wait until the fly 
Pig. o.— White fly {Aleyrodes dtri): a, Winged male 
insect . with enlarged view of terminal segments 
;it /;.- r. dorsal view of winged female, with enlarge- 
ments of ovipositor, bead, antenna, wing margin, 
and leg al d, e,f, g, h,i. (Reduced from Riley and 
BowardJ 
a See discussion oi this subject, pp. 9-14. 
