THE CANADIAN ENTOMOLOGIST. 147 



completely closed at the apex. Abdomen spatulate, as long as the 

 thorax, the first dorsal segment very finely but distinctly rugulose; 

 second segment with a distinct transverse suture before the middle, 

 which does not extend quite to the margins; the surface before the 

 suture and for one-third of the distance beyond distinctly rugulose; 

 segments beyond the second smooth. General color shining black; 

 mandibles and palpi slightly fuscous; teguhe testaceous; wing veins 

 and stigma brownish ; legs testaceous, their coxae piceus. Abdomen 

 wholly black. 



Type locality. — Tempe, Arizona. 



Host. — Agromyza piisilla. 



Type No. 15592, United States National Museum. Two male 

 specimens from the type locality, labelled Webster, No. 7215. — 

 V. L. Wildermuth, collector. 



Distinguished from 0. aridus by the presence of a distinct 

 transverse furrow on the second segment and by the rugulose 

 sculpture of that segment. May possibly be the male of 0. nanus 

 Prov., from the type of which it differs, however, in the smooth 

 propodeum and the wholly black abdomen. 



Opiiis arid is, n. sp. 



Female. — Length, 1.25 mm. Head perfectly smooth and 

 polished, the fac(i moderately hairy; vertex, temples and occiput 

 with sparse, inconspicuous hairs; clypeus arcuated apically, leaving 

 a distinct opening between it and the mandibles; antenna? some- 

 what longer than the body, 18-jointed in the type (varying from 

 18-jointed to 23-jointed in other specimens of the series), the first 

 joint of the flagellum slightly the longest. Thorax smooth and 

 polished; mesonotum without a median depression or furrow be- 

 fore the scutellar fovea, parapsidal furrows impressed at the an- 

 terior lateral angles of the mesonotum, but not attaining to the 

 disc; mesopleurae smooth, with a shallow, ovate, non-foveolated 

 impression below the middle; propodeum moderately hairy, nearly 

 smooth ; the apical margin very slightly roughened. Wings denseh- 

 ciliated, giving them a brownish tinge; stigma lanceolate, the 

 radius arising before the middle, and attaining the wing margin 

 above the extreme wing apex; its first abscissa shorter than the 



