58 THE SPRING GRAIN-APHIS OR " GREEN BUG." 



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. Antennas 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. 



