MOLTING. 61 
present. The size varies greatly in nearly all forms, wingless viviparous females 
varying from 1.5 mm. to over 2 mm. 
Measurements of antennal joints (average for 8 specimens): X, 0.069 mm.; II, 
0.045 mm.; Ill, 0.210 mm.; IV, 0.135 mm.; v^ 0.140 mm.; VT, base, 0.089 mm. 
VI, filament, 0.305 mm.; total length, 0.993 mm. 
Pupx (fig. 14). — Measurements of antennal joints (average from 8 specimens): 
I, 0.064 mm.; II, 0.056 mm.; Ill, 0.186 mm.; IV, 0.127 mm.; V, 0.134 mm.; VI, 
base, 0.090 mm.; VI, filament, 0.270 mm.; total length, 0.927 mm. 
Winged viviparous female (fig. 7). — Measurements of antennal joints (average from 
8 specimens): I, 0.082 mm.; II, 0.059 mm.; Ill, 0.300 mm.; IV, 0.223 mm.; V, 
0.215 mm.; VI, base, 0.110 mm.; VI, filament, 0.395 mm.; total length, 1.384 mm. 
MOLTING. 
The time required for molting, from beginning to completion, is 
30 minutes. The first indication is restlessness; the antennae are 
waved continuously and the legs move jerkily. This period of 
restlessness continues for 10 minutes, after which the antennae are 
allowed to come to rest close down upon the dorsum. A few minutes 
later the tip of the abdomen will appear transparent and baggy, due 
to the old skin having slipped backward; the head and eyes are now 
being freed. It appears that the skin first ruptures in the cephalic 
region and only splits a part of the length of the dorsum, the insect 
gradually working its way out from this extremity. After the head, 
the antennas are the first to be liberated, then each pair of legs in 
succession, and after all of the appendages have been freed the insect 
has still to struggle somewhat to free its abdomen. These observa- 
tions were made on individuals casting the third or fourth molt. 
NUMBER OF MOLTS. 
Quite a number of observations were made on the number of molts 
and the period between the same, it being learned that stem mothers, 
the summer forms, and the sexes molt 4 times only. 
To facilitate careful and accurate observations upon the number of 
molts, a young wheat plant was potted in a 5-inch flowerpot. A 
circle of black paper was cut small enough to fit down in the top of 
the pot. A small hole was then cut in the center and the paper disk 
was then fitted closely down about the base of the plant. After the 
paper was in place the space immediately around the plant was filled 
in with absorbent cotton made black with waterproof ink. Then a 
young Toxoptera that had just been born was placed on the plant 
inclosed by a clean lantern globe, with a piece of new cheesecloth 
firmly secured over the top to prevent the grayish cast skins from 
being overlooked. Each cast skin was removed as soon as the molt 
was completed, and a record made so that it could not possibly be 
counted a second time. All observations recorded in the notes on 
molting were made in this manner, 
