Psilopa petrolei, new species.

black, polished, not light coloured, pruinose except the lower part of the occiput, cheeks and sides of face, which are thinly grayish pruinese; halteres yellowish, the knobs white. Eyes densely hairy, most approximate at middle of face. Third joint of antennæ slightly longer than the second, the spine of the latter not reaching beyond the apex of the antennæ. Wings hyaline, tinged with gray on nearly the costal half, except sometimes a spot toward apex of the submarginal cell; apex of second vein nearly twice as far from the first as from the apex of the third vein. Length, 2 mm.