THE BLACK FLY OF CITRUS. 31 
the average was 32.19 eggs per spiral. However, the number of eggs 
laid in the laboratory on young shoots brought in from the field on 
which the adults had gathered was 26 per spiral, as against 36 for 
eggs laid on the leaves out of doors under natural conditions. Furth- 
ermore, out of 50 spirals laid in the laboratory only 8 had above 30 
eggs and only 3 above 40, whereas out of the same number of 
spirals laid in the field 28 had above 30 eggs and 20 above 40. 
Hence, the normal number of eggs per spiral is between 35 and 50. 
Since different females have been observed to lay eggs as soon as 18 
hours after emergence from the pupa case and as long as 4 days after, 
emergence, there is but one conclusion, namely, that more than one 
spiral or mass of eggs is laid and that a single female may lay con- 
siderably over 100 eggs in her lifetime. If this were not the case, 
in view of the high mortality, especially in the early stages of devel- 
opment, it is doubtful if Aleurocanthus woglumi would be a pest of 
even secondary importance. 
The individual egg is canoe shaped with its ends rounded. It is 
attached to the leaf by a short pedicel situated near its posterior end. 
When first laid the eggs are creamy white with what appears to be a 
reticulation of the surface, but in 36 to 48 hours they become brown 
in color, the reticulate appearance disappears, and they become 
blackish between the eighth and tenth days. In from 11 to 20 days 
the eggs hatch, the larvae crawling forth through a slit along the 
median dorsal surface of the egg, the brown eggshell remaining plump 
and often very confusing as the slit seems to close again. Drying out 
of the leaves on which the eggs are laid seems to kill them, until one 
or two days before they are ready to hatch, as is shown later. 
FIRST LARVAL INSTAR. 
The larva that emerges from the egg is rather elongate ovate in 
shape, whitish in color, with reddish eye spots, short antennae, and 
rather short legs. It crawls around sluggishly for from two to four 
hours and then settles down, the farthest distance crawled, out of 
580 individuals, being 1^ inches from the center of the egg spiral. 
But fully 80 per cent of the larvae never crawl more than one-half 
inch away from the spiral from which they emerge. On settling 
down the larva describes an arc of from 75 to 120 degrees, evidently 
to help in inserting its thread-like rostral setae into the tissues of the 
leaf. This movement seldom lasts more than 20 minutes. Two 
hours after emergence from the egg the larvae are dusky all over, 
with the exception of the margins, and within four hours they are 
fully colored, i. e., blackish, and more broadly ovate than on 
emergence. There is a tendency for them to flatten out. There is a 
pronounced median ridge, on each side of which, anteriorly and pos- 
teriorly, are four long dorsal spines and numerous shorter ones. 
Larvae that have settled once have been observed to change their 
