374 



ENTOMOLOGICAL NEWS. [Dec, 'o6 



species are at hand for comparison, the agreement of our form 

 with Professor Mik's description makes us believe the two 

 forms to be congeneric. Like so many of the other Diptera 

 living on the sand,* Parathalassius is conspicuous by its dense 

 coating of pollen. Even the hairs and bristles are glistening 

 white, so that the males especially, when viewed from in front, 

 are ornate with a silvery sheen. 



The European species (P. blasigii) possesses several con- 

 spicuous white hairs on the under side of the hind femora, and 

 these are lacking in the California form. Moreover, in blasigii 

 the first posterior cell is narrowed at its apex. Otherwise, our 

 species tallies well with Mik's description. 



Parathalassius aldrichi sp. nov. 



Male. — Length, 2.75 mm. — Entirely silvery-gray pruinose, all the 



bristles white. Vertex broad, concave, silvery pruinose: ocelli widely 

 separated; one pair each of vertical, frontal, 

 and ocellar bristles ; face very narrow below the 

 antennae, concave, broadening at the convex 

 clypeus, closely covered with short silvery- 

 white pubescence, lower facets of eyes large, 

 those of the lowermost third concealed by a 

 dense covering of silvery-white scale-like hairs. 

 Eyes not at all emarginate at antennas. Antennae 

 black, three-jointed, though the first two joints 

 are minute, third joint short-oval, pointed, with 

 a long terminal bristle-like arista. Occiput sil- 

 very-gray pruinose, occipital bristles seriately 

 arranged below, and forming a ciliate fringe 

 Parathalassius aldrichi to the eyes. Proboscis and palpi minute, 



and face of male. blackish. 



Thorax silvery-gray pruinose, the dorsum with scattered short white 

 hairs, and with eleven pairs of short achrosticals, six pairs of long 

 dorsocentrals, three pairs of supra-alar and three long humeral and 

 posthumeral bristles: scutellum with four marginal bristles, no pleural 

 bristles. 



Abdomen short, with numerous white hairs, when viewed from above 

 or the right, with but four visible segments, the second segment longest 

 and bearing a basal transverse row of black pores. Hypopygium very 

 large and globular, comparativey bare though pruinose, asymmetrical, 



*e. g. Lipochaeta, Thinophila, Thcreva, Stichopogon, etc., and the 

 Empidid genera Schistostoma, Coloboneura, Halsanalotes, and Cherso- 

 dromia. 



