58 THE SPRING GRAIN-APHIS OR 
STEM MOTHERS. 
At both Richmond and La Fayette, Ind., the eggs begin to hatch 
the latter part of March and continue until about April 10. The 
first generation, or stem mothers, differs from the next generation 
slightly in coloration, and there are besides some slight structural 
differences. The measurements of the body are not included in the 
following description, as the specimens are mounted in balsam. 
DESCRIPTION OF THE DIFFERENT INSTARS. 
First instar. — Before first molt: General color, very dark Nile green; head, beak, 
antennae, legs, and cornicles very dark gray; tips of the antennas, the tarsi, and the 
eyes black. Antennae 4-segmented. 
Measurements of antennal joints (average from 2 specimens): I, 0.034 mm.; II, 
0.034 mm. ; III, 0.093 mm. ; IV, base, 0.046 mm. ; IV, filament, 0.114 mm. ; total length, 
0.321 mm. 
Second instar. — Before second molt: General coloration of head and body lighter 
than in the preceding stage, otherwise the coloration the same. Antennae 5-segmented. 
Measurements of antennal joints (average from 3 specimens): I, 0.045 mm.; II, 
0.039 mm.; Ill, 0.127 mm.; IV, 0.082 mm.; V, base, 0.066 mm.; V, filament, 0.161 
mm.; total length, 0.520 mm. 
Third instar. — Before third molt: The color of the body now varies from pale green 
to deep apple green; head concolorous with body; legs slightly lighter; eyes, tip of beak, 
tip of cornicles, articulation of femora, and tibiae black; distal two-thirds of antennae 
black; basal portion greenish gray. Antennae 5-jointed. 
Measurements of antennal joints (average from 4 specimens): I, 0.050 mm.; II, 
0.045 mm.; Ill, 0.152 mm.; IV, 0.093 mm.; V, base, 0.072 mm.; V, filament, 0.174 
mm.; total length, 0.586 mm. 
Fourth instar. — Before fourth molt: General coloration variable, though about the 
same as in third instar, with the exception that the eyes of the young begin to show 
through the body wall; eyes and tip of beak black; legs greenish gray, the articulation 
of femora and tibiae and the distal portion of tibiae very dark, and tarsi black; cauda 
lighter than the body, as is sometimes also the head ; the two distal segments and distal 
portion of third segment of antennae black, gradually shading off until at the base they 
are concolorous with the head; cornicles black at tips, shading off into pale grayish 
green at base. Antennae 5-jointed; sometimes, however, there are 6 distinct joints. 
Measurements of antennal joints (average from 4 specimens): I, 0.065 mm.; II, 
0.051 mm.; Ill, 0.194 mm.; IV, 0.119 mm.; V, base, 0.088 mm.; V, filament, 0.196 
mm.; total length, 0.713 mm. 
Fifth instar. — In the adult stage the color varies from a clay yellow to greenish yellow 
and deep apple green; there is no central dorsal stripe; the eyes of the young show 
through the body walls. In some of the greener specimens the head is slightly lighter 
and in some of the lighter colored specimens the head is slightly darker than the body; 
eyes and tip of beak black; legs pale greenish gray, the articulation of femora and 
tibiae and the distal third of tibiae quite dark; tarsi black; cauda in yellow specimens 
with a yellowish tint and in the deep green specimens somewhat grayish, shape and 
length same as in summer form; cornicles concolorous with body except the distal 
third, which is black, shape and length same as in summer form; three distal segments 
of antennae and distal half of fourth black, the basal joints concolorous with the head. 
Antennae 6-segmented, though two specimens were found in which one antenna of each 
was only 5-segmented. 
