THE PEA APHIS WITH RELATION TO FORAGE CROPS. 



19 



Measurements (average) from three specimens, immediately after 

 placing in balsam and before shrinkage occurs: Length of body, 

 2.79 mm., to tip of cauda, 3.18., width, 1.11; length of wings, 3.51 

 mm., width, 1.16; length of cornicles, 0.84 mm.; length of cauda, 

 0.46 mm.; length of hind tibia, 2.32 mm. Measurements of antennal 

 segments : 



I. 



II. 



III. 



IV. 



V. 



VI, base. 



VI, fila- 

 ment. 



Mm. 

 0.156 

 .156 



Mm. 

 0.069 

 .078 



Mm. 

 0. 826 

 .817 

 ' 1.006 



Mm. 

 0.721 

 .730 

 .716 

 .677 

 .658 

 .658 



Mm. 

 0.748 

 .748 

 .735 

 .735 

 .658 

 .677 



Mm. 

 0.304 

 .296 

 .329 

 .310 

 .310 

 .290 



Mm. 

 1.095 

 1.061 

 1.006 

 .987 

 .968 







1.006 







.968 

 1.045 













SEXUAL FORMS. 



Winged male (fig. 7).- — (Described from two specimens, Dec. 4, 

 1912.) Head and pro thoracic segment gamboge with a dusky to 



Fig. 7. — Macrosiphum pisi: Winged male, much enlarged; c, antenna of same, more enlarged. (Original.) 



brownish longitudinal median dorsal marking which does not extend 

 quite to tip of head. Thoracic shield brownish with interstices con- 

 colorous with head. Abdomen pale green with pale dusky markings 

 as shown in the illustration (fig. 7) and the segments posterior to the 

 cornicles pale yellowish green. Eyes very dark red, almost black. 

 Antennae (fig. 7, a) noticeably longer than body; filament of VI longer 

 than III; entire antenna blackish excepting segments I and II and 



