THE PEA APHIS WITH RELATION" TO FORAGE CROPS. 



13 



fourth of V, distal half of VI, base and all of filament of VI, which 

 parts are black; segment III sometimes, but not always, bearing a 

 small inconspicuous sensorium near its base and the usual sensoria 

 at distal end of V and VI 

 base. Beak just reaching 

 coxae of second pair of legs. 

 Legs with femur very pale 

 green and semi transpar- 

 ent; tibia with basal hah 

 pale semitransparent, the 

 distal half with a faint 

 brownish tint and the tip 

 black; tarsus black. Cor- 

 nicles reaching tip of cauda 

 (of the four specimens ex- 

 amined the cornicles 

 reached a little beyond the 

 tip of cauda in three speci- 

 mens and not quite to the 

 tip in the fourth specimen) , 

 concolorous with body at 

 base, becoming paler and 

 semitr ansparent toward 

 the apex, the tip blackish; 

 cylindrical and slender; noticeably widened at base and the tip imbri- 

 cated. Cauda ensiform and typical of the genus, and concolorous 

 with body. 



Measurements from two specimens immediately after placing alive 

 in balsam and before shrinkage occurs: Length of body, 2.63 mm., to 

 tip of cauda, 3, width, 1.45; length of cornicles, 0.74 mm., of cauda, 

 0.44. Measurements of antennal segments: 



Fig. 2. — Macrosiphum pisi: Adult stem-mother. Much en- 

 larged. (Original.) 



I. 



II. 



III. 



IV. 



V. 



VI, base. 



VI, fila- 

 ment. 



Mm. 



Mm. 



Mm. 



Mm. 



Mm. 



Mm. 



Mm. 



0.156 



0.069 



0.695 



0.348 



0.469 



0.235 



0.522 



.156 



.078 



.695 



.348 



.452 



.243 



.539 



.139 



.078 



.626 



.287 



.400 



.209 



.469 



.139 



.087 



.634 



.296 



.400 



.209 



.469 



SUMMER VIVIPAROUS GENERATION. 



First instar, before first molt and about 1 hour old (fig. 3). — (Described 

 from six specimens, Aug. 20-21, 1912.) Head and thoracic segments 

 whitish with a pale greenish tint; remainder of body pale green 

 excepting those segments posterior to and including the segment 



