Brachycistis gaudii, n. sp.—♀. Length about 6½ mm.; shining black, brown on prothorax, at bases of wings, and at extreme (usually covered) bases of abdominal segments; antennæ long, dull reddishbrown, first joint of flagellum equal to second; head broader than thorax; eyes very prominent; ocelli in an equilateral triangle, the area between them elevated; edge of clypeus, and mandibles, dark ferruginous, the latter tridentate; mesothorax shining, hairs and punctures very sparse; metathorax minutely transversely lineolate; tegulæ light ferruginous; wings hyaline, iridescent, nervures pale except the costal, stigma large, dark brown; three submarginal cells and two recurrent nervures, the second recurrent sometimes failing below; marginal cell extremely short, broader than long, its greatest diameter about half length of stigma; first submarginal large, extending along stigma to marginal; second submarginal minute, triangular, entirely cut off from marginal; third submarginal minute, long and narrow, its tip reaching marginal; first recurrent nervure joining first transverso-cubital, second joining third submarginal cell near its base; abdomen shining, very sparsely punctured, with long sparse yellowish hairs; first segment swollen, about twice as long as broad, with a deep constriction between it and the second; apical curved spine long, ferruginous; legs black, knees, apices of tibiæ and tarsi light brown.