THE BLACK FLY OF CITRUS. 33 
The early second larval instar individual is whitish In color, more 
ovate than in the preceding instar, and more or less flattened, with 
the eye spots and vasiform orifice quite prominent. Within three 
to four hours after molting the second larval instar becomes fully 
colored, i. e., dull black with the exception of a large, more or less 
circular spot on the anterior part of the dorsum, which remains a dull 
green. The insect is also decidedly more convex than in the preceding 
instar and the spines are more numerous and more prominent. The 
cast skin usually, though not always, remains attached to the long 
dorsal spines and rests near the middle of the dorsum of the second 
larval instar individual. 
The duration of this instar ranges from 5 to 30 days in laboratory 
individuals, though the maximum time that has been observed out 
of doors is 21 days. The large majority of individuals molt between 
the eighth and thirteenth days. 
Just before the second molt a color change takes place, which is 
noticeable from 18 to 30 hours before the skin is shed. This may be 
due to the distention of the individual at this time. Instead of a 
circular greenish area on the anterior dorsum one finds a crescentic 
black area anteriorly and a horseshoe-shaped area posteriorly and 
the green area more or less cruciform. The margin of the insect is 
whitish, just as it is in the premolting period of the first larval 
instar. 
In life-history studies conducted by the writers, out of 390 indi- 
viduals that entered this stage, 84, or about 21.5 per cent, died. 
THIRD LARVAL INSTAR. 
The procedure in the second molt is the same as in the first, although 
the various stages in this process are more rapid and of shorter 
duration; the duration of the entire operation from the splitting of 
the skin to the complete cessation of the rotating and " cupping up" 
movements is from 15 to 20 minutes. The movements, though 
more easily observed than in the first molt, do not seem to be nearly 
as violent. 
The time required for individuals to become fully colored, i. e., 
shiny black, is from one and one-half to two hours. The only portion 
of the body that does not become black is a more or less hemispherical 
dull green spot on the anterior part of the dorsum, situated over the 
greater part of the thorax and the anterior part of the abdomen. 
The spines are more numerous and stouter than in the second larval 
instar and the cast skin of the preceding stage (and often stages) 
remains attached to or entangled in the spines of the middle part of 
the dorsum. The convexity of the individuals becomes pronounced 
and the insect is distinctly ovate in outline. 
185528°— 20 3 
