1909] Two New Genera and Species of Aphididae 197 



projection near the distal end (PI. XXVII, Fig. 2). Two or more 

 prominent finger-like tubercles on the dorsum of the abdomen. 

 Cornicles moderately long and dilated at the base. Style small and 

 globular. 



Sporadic in hal)it. Wingless viviparous adults unknown. 



Phymatosiphum monelli, n. sp. 



I am indebted to Mr. J. T. Monell for the specimens from 

 which this species is described, as well as for the very complete 

 color notes. Mr. Monell has collected this species annually for 

 the past few years in the months of May and June in St. Louis, 

 Mo., on the Ohio buckeye {Aescuhts glabra). Nearly thirty years 

 ago he also collected what was perhaps this species, although pos- 

 itive determination is impossible owing to the loss of the spec- 

 imens. I quote the following from Monell's note: "No. 266X 

 Oct. 5, 1879: Two dry specimens taken on the underside of 

 lea\-es of the buckeye. One winged, general color of dorsum and 

 antennae light fuscous brown. Short tail yellow. Two tuber- 

 cles on abdomen. One winged, head and thorax light fuscous, 

 the basal half of the abdomen occupied by a dusky transverse 

 band, the apical half lighter, tail yellow. Body of winged more 

 or less pulverulent." To the naked eye it closely resembles 

 P. acerifolii Thos., but is readily distinguished by the single pair 

 of dorsal abdominal tubercles, acerifolii having four pairs of these 

 tubercles. It lives sporadically on the under surfaces of the 

 leaves. Mr. Wilson writes that he has found this same species 

 in Washington, D. C. 



Descriptions: Winged viviparous female: To the naked eye this 

 species resembles P. acerifolii. The head is brown with prominent 

 frontal antennal tubercles (PL XXVII, Fig. 3). Antennse brownish 

 with a dusky to black ring at the distal ends of segments III, IV, V, 

 and base VI. Segment I large compared with II; III about one and 

 one-half times as long as IV; IV and V subequal, V usually being very 

 sHghtly the longer; base VI short, less than the length of I ; filament \'I 

 longest, being about a half longer than III; total length greater than 

 twice that of the body. 9 to 15 (usually 11 — 13) roundish sensoria in 

 a row on the basal half of III, one large circular sensorium at the 

 distal end of V, and several surrounding a larger one at distal end of 

 base VI (PI. XXVII, Fig. 4) . Eyes brilliant red, ocelh three in number 

 and prominent. Beak rather short, not reaching to the mesocoxa^. 

 Thorax concolorous with the head. Wings hyaline, excepting in the 

 fore wings a small dusky patch at the end of each vein, at the base of 

 the stigmal vein, and the stigma which is dark brown with a clear 

 central spot; venation frail, pale yellowish brown, subcostal dusky 



