IX 
larval pellicle, several skins are shed, the later ones being pushed out from be- 
neath the seale. The male comes forth a delicate two-winged insect with six legs, 
without food-taking apparatus, and bearing two simple eyes in the usual position 
for the mouth. 
The life-history of but few of these scales has been carefully worked out. 
This phase of the subject offers a fertile and profitable field for biological study. 
Genera. 
A. Scale of female circular, exuvise central or approaching the margin. 
1. Scale of male oblong; color and texture similar to that of female; 
exuviae centrally located, sometimes noticeably nearer one of the 
extremities. Aspidiotus. 
2. Seale of male elongated ; exuvia? at one extremity. 
(a) Male seale white and earinated. Diaspis. 
B. Scale of female elongated; exuvia; terminal. 
1. Scale of male white, shorter and narrower than female scale. In 
pygidium five groups of circumgenital glands present. Chionaspis. 
2. Scale of male similar in form and texture to that of female. Mytilaspis. 
3. Scale of female shows distinctly two moulted skins. Scale of male nar- 
row, elongate; scale of female sometimes oval. Parlatoria. 
TABLE FOB DETERMINATION OF SPECIES. 
Aspidiotus. 
A. Female pygidium with three pairs of lobes. 
B. Third lobe much reduced or only a pointed prominence. 
C. Size of scale 1% to 2 mm.; scale somewhat convex. fernaldi. 
CC. Size of scale 2% mm.; scale flat. juglans reyiae. 
BB. Third lobe about same size as second lobe. 
C. Three pairs of incisions (see Plate VI, fig. 25), with distinct chitinous 
processes and 5 groups of spinnerets; plates simple and inconspicuous; 
exuvia; black under, yellowish brown covering. obsciirus. 
CC. No incisions or chitinous processes; 4 groups of spinnerets; plates con- 
spicuous and toothed; exuvia; covered with thin yellow film. 
hederae nerii. 
AA. Female pygidium with less than 3 lobes. 
B. Female pygidium with third pair of lobes wanting. 
C. Spinnerets present, median lobes converging at the tip; chitinous pro- 
cesses unequal, inner one larger (see Plate I, fig. 1) ; scales arranged 
in clusters; exuviae of male seale yellowish ivhcn rubbed. forbesi. 
CC. Spinnerets wanting; median lobes but slightly converging at the tip; 
chitinous processes equal (see Plate V, fig. 19) ; exuvia; of male scale 
black when rubbed. pernieiousus. 
BB. Female pygidium with 2d and 3d pairs of lobes wanting or rudimentary. 
C. Spinnerets present. 
D. Four groups of spinnerets. 
E. Scale light in color; exuvia; naked, pale straw color; plates toothed. 
greenii. 
EE. Scale dirty gray; e.xuviie orange-colored, covered with gray; plates 
simple. osborni. 
DD. Five groups of spinnerets. 
E. Exuvia; orange-colored; scale dark gray. 
