Mesostenus Nubilipennis.–♀. Black ; anterior orbits, lower part of cheeks, spot on middle of face, most of clypeus and labrum, spot on mandibles, annulus on antennæ, line on sides of collar, spot on each side of prothorax above, spot on disk of mesothorax, most of scutellum, dot on post-scutellum, tegulæ, spot beneath, spot on sides of pleura, spot on each side behind posterior wing, two elongate marks on metathorax behind covering the prominent, obtuse and transversely compressed tubercles, the four anterior coxæ, spot on posterior pair above, annulus at base of posterior tibiæ, extreme base and apex of the first joint of posterior tarsi, the second, third and fourth joints entirely, and the apical margin of segments 1-6 of abdomen, all white ; front unarmed ; thorax opaque; mesothorax confluently punctured ; metathorax reticulated; wings hyaline, with a fuliginous cloud beneath stigma, areolet quadrate, closed; legs fulvous, extreme tips of posterior femora, their tibiæ except white annulus near base, most of basal joint of their tarsi, and the apical joint, black ; abdomen fusiform, rather shining, punctured, first segment considerably dilated at apex ; ovipositor shorter than abdomen.