AMERICAN HYMENOPTERA. 87 



along the eyes; vertex black, moderately shining, with sparse, broad, flat-bottomed 

 punctures. Antennse brownish yellow, 13-j()inted, about three-fourths the length 

 of the body; the fourth joint is a little longer than one-half of the third ; joints 

 four, five and six are nearly of the same length ; the following joints are some- 

 what shorter ; the last joint is about equal to the two i)receding taken together. 

 Thorax black, moderately shining, with very rough, but not very dense trans- 

 verse rugosities; pubescence short and very sparse; parapsidal grooves well 

 marked, punctured at the bottom ; scutellum coarsely sculptured : its basal fovese 

 are indistinct; the smooth space of the pleurae is almost entirely acicuiate; 

 scapuUe brownish yellow. First segment of the abdomen longitudinally striate ; 

 the second segment concealing all the following, has the shape of an elongated 

 oval when seen from above; seen from the side its longitudinal diameter dis- 

 tinctly exceeds the transverse one; the ventral valve, ending in a short, pubes- 

 cent point, usually projects beyond the edge of the second segment, its angle is 

 about 60° or 70° ; abdomen polished, black ; ventral valve yellowish brown ; feet 

 brownish yellow; hind tibiie and a part of the first joint of the hind tarsi infus- 

 cated ; tips of all the tarsi brownish ; veins of the wings brownish ; areolet rather 

 small, its structure like that of the following sj)ecies (S. ctimpanubi). 



"Male. — 0.10 long; antennai 15-jointed, third joint excised below, fourth half 

 as long as the third ; head yellow, except a black spot on the vertex, whi(^h in- 

 cludes the ocelli ; a part of the collare and of the pleune also yellow, which color 

 seems to be variable in extent in different specimens; abdomen truncate at the 

 tip, bell-shaped wlii-n seen from the side; the sculpture of the head and thorax 

 and the coloring of the feet are the same as in the female." 



Baron Osteii Sacken did not know the galls IVoni which he ob- 

 tained his specimens. The specimens in my collection I bred from 

 Avoody twig galls taken at Lansing, Mich., on red oak and no true 

 gall-tiies were reared. The flies issued in large numbers and vary 

 much in color, especially in the females. The females also vary from 

 one and a half to three mm. in length. The darkest of these show 

 a slight rufous coloration only on the lower portion of the face, about 

 the eyes and a small spot in front of the tegulse ; light ones have the 

 whole head, except a dark spot on the vertex, the neck, and a large 

 space on the shoulders, bright rufous as in the males. 



This species is quite close to lignicola O. S., but differs from that 

 species in having a very coarsely transversely Avrinklcd mesonotum. 



SyiK'd'giis bi(*olor Ash. 



Si/nerfjun bicolor Ash., Trans. Am. Ent. Soc. xii, 1885, p. 302, 9 %• 

 Synerfiua bicolor Crcsson, Syno]>. Hymen. Amer. 1887, p. 180. 

 Synergus bicolor De Dalle Torre, Cat. Hymen, ii, 1893, p. 110. 

 " Length .12-. 14 inch. Head, thorax, antennse and legs yellowish ; thorax and 

 legs finely rugoso-punctate ; a small brown blotch on vertex of head and a medial 

 stripe on mesoscutum and along the hinder edges; antennse 1.5-jointed in male, 

 13-joiutcd in female; abdomen polished black; wings hyaline, veins yellowish." 

 i\[r. Ashmead's specimens were bred from the galls of Andricns 

 folidtn.i Ash. 



TR.\NS. AM. ENT. SOC. XXIII. . MARCH, 1896. 



