58 WHITE FLIES INJURIOUS TO CITRUS IN FLORIDA. 
Proportion of eggs that hatch. — Observations covering many thou- 
sands of eggs, both in the cage experiments and in the grove, have 
demonstrated that the number of eggs that fail to hatch is too insig- 
nificant and has too little practical bearing to warrant the collection 
of data on this point. It is safe to say that considerably less than 1 
per cent do not hatch. In fact, it seems evident that no egg would 
fail to hatch except owing to the dropping of the leaf or unless sub- 
jected to attack from without. In many instances failure to hatch 
can be directly traced to attack by several species of insects and a 
fungous parasite. 
Effect of drying of leaves on hatching. — In 10 instances leaves bearing 
many thousand eggs were so placed that the eggs were exposed to 
direct sunlight or to partial shade, and although frequent observa- 
tions were made none of the eggs were known to hatch. In general 
the drying of leaves to which eggs are attached prevents hatching of 
all except those eggs containing nearly mature embryos. This fea- 
ture is probably common to all aleyrodids, since the senior author 
has noted a similar occurrence in the case of the greenhouse white fly 
(A. vaporariorum) . 
The Larval and Pupal Stages, 
description of stages. 
THE LARVA. 
The larva? * are thin, translucent, elliptical, scalelike objects, found 
usually on the underside of the leaves, though more rarely upon the 
upper surface. When normally attached to the leaf they are so 
nearly transparent as to be seen with difficulty. They readily 
become visible, however, by either bending or rubbing the fingers 
along the opposite side of the leaf, thus loosening them and allowing 
the air to get beneath them. They then appear whitish (PL X, fig. 2). 
So very inconspicuous are the live larvae and their attack so unac- 
companied by any visible effects on the leaves, aside from the black- 
ening of the foliage, that their presence is very frequently overlooked 
by the casual observer. A detailed description follows: 
First instar larva (figs. 4-6). Length, 0.3 to 0.37 mm.; width, 0.182 to 0.22 mm. 
Body flat, scalelike, somewhat swollen ventrally, especially in the cephalothoracic 
region; margin entire, with 30 small tubercles, each bearing a horizontally directed 
spine of which 6 cephalic and 4 anal are proportionately longer. Spines of second 
pair, counting from anterior end of body, arising from tubercles not on, but slightly 
posterior to, margin on ventral surface. Relative lengths of the 15 pairs of spines as 
follows: 
Pair 1 _2_^Jt 5 6 7 10 11 12 13 14 15 
Spaces ll' 9.8' ll' 6.5' 5.4' 5.5' 6' 4' 4' 4 ' 18' 5.4' 18.5' 
1 The larvae and pupae are frequently called by many growers the "egg" of the 
white fiy. This misapplication of terms should be discouraged as it leads to unde- 
sirable confusion when referring to the various stages through which the white fly 
passes during its growth from egg to adult. 
