986 
Journal of Agricultural Research 
Vol. V, No. ai 
Second instar. —Morphological characters: Antennae as follows: I, 0.024 mm.; 
II, 0.032 mm.; Ill, 0.064 tnm.; IV, 0.056 mm.; V, base 0.048 mm., unguis 0.096 mm.; 
segments with the characters of first instar, excepting that the distal sensorium is on 
segment IV. Compound eyes with about 18 facets. Cornicles short. Legs some¬ 
what similar to those of the previous instar, hind tibiae 0.192 mm. long. 
Color characters: Similar to those of the previous instar. Tarsi, distal extremities 
of tibiae, and distal extremities of antennae black. 
Third instar. —Morphological characters: Antennae as follows: I, 0.032 mm.; II, 
0.04mm,; III,o.ii2 mm.; IV, 0.08 mm.; V, base 0.064 mm., unguis 0.112 mm. 
Armament of the antennae, legs, etc., as in previous instar. 
Color characters: As in previous instar. 
Fourth instar. —Morphological characters: Antennae as follows: I, 0.041 mm.; II, 
0.041 mm.; Ill, 0.08 to 0.144 mm.; IV, 0.056 to 0.128 mm.; V, 0.072 to 0.112 mm.; VI, 
base 0.064 to 0.08 mm., unguis 0.128 to 0.176 mm.; segments III to VI imbricated 
and armed with a few stout hairs; segment V with a distal sensorium and VI with 
the usual group at base of unguis, otherwise the segments are similar to those of pre¬ 
vious instar. Compound eyes with very many facets. Cornicles cylindric and 
imbricated, 0.072 to 0.096 mm. in length. Legs with many prominent spines, tarsi 
imbricated, tibiae 0.368 to 0.448 mm. long. 
Color characters: General color characters similar to those of third instar. Black 
marking only on the distal extremities of the antennae, the distal extremity of the 
labium, the cornicles, the tarsi, and the distal extremities of the tibiae. 
Fifth instar (adui,t). —Morphological characters: Antennae (PI. LXXIV, fig. 9) 
as follows: I, 0.045 mm,; II, 0.045 mm.; Ill, 0.16 to 0.184 mm.; IV, 0.128 to 0.168 
mm.; V, 0.112 to 0.144 mm.; VI, base 0.081 mm., unguis 0.184 to 0.232 mm.; segments 
III to VI strongly imbricated and armed with numerous stout hairs; segment III 
with 7 to 10 irregularly placed sensoria, the arrangement of these giving the segment 
a slightly knotty appearance; segment IV with about an equal number of sensoria 
irregularly arranged; segment V with about 5 sensoria of unequal size and with irregu¬ 
lar arrangement; segment VI with the usual group at the base of the unguis. Vertex 
slightly rounded. Eyes with distinct ocular tubercles; thorax with a very prominent 
tubercle; abdomen with four lateral tubercles on each side, the pair caudad of the 
cornicles and the most cephalic pair larger than the others. Cornicles (PI. LXXIV, 
fig. 13) cylindric, imbricated, slightly flanged distad, 0.104 to 0.28 mm. in length. 
Legs slender, hind tibiae 0.496 to 0.592 mm. long. Cauda conical, not constricted, 
setose, and armed with long curved hairs. Anal plate somewhat truncate; genital 
plate rounded, wrinkled, and spiny; claspers irregular, corrugated, covered with 
minute spines; penis long, curved, fleshy (PI. LXXIV, fig. 8). Length from vertex 
to tip of abdomen, about 1.12 mm. Shape of insect elongate and narrow, much more 
so than any other form. 
Color characters: General color greenish brown, occasionally olive, sometimes with 
an orange tinge. Antennae, cornicles, cauda, and genital appendages black; crown 
with a black cap similar to that of the stem mother; tip of the labium smoky to 
black. Insects sometimes slightly pruinose. 
FIRST APPEARANCE OF SEXES 
The production of the sexes is governed apparently by two factors, 
the season (temperature being of prime importance in this factor) and 
the generation. Of these the first is by far the more important. 
The earliest sexes in breeding cages were bom on September 2. They 
were in the eleventh generation, which was also the earliest generation in 
