8 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 30 Ser. 



Osten Sacken says that the lower edge of the face is nearly 

 on a level with the lower corner of the eyes. P. jlahellifer 

 has black legs; P. suferbus and P. castus have yellow 

 legs. 



Hercostomus Loew. 



The two species described below are referred with con- 

 siderable doubt to this genus, which was not very clearly 

 defined by Loew. Hercostomus was to him a general depos- 

 itory for several species which would not fit into the gen- 

 era Gymno-pternus, Pelastoneurus, Paraclius and Hyfo- 

 ■phyllus. Hercostomus was regarded as "not ripe as yet 

 for further subdivision on account of the insufficiency of 

 our knowledge of its species." The two species here 

 described differ from Gymnopternus in the structure of the 

 hypopygium, and resemble Hercosto?nus in neuration. I 

 have not seen fit to establish new genera on them, although 

 this may yet be necessary. Both the species are from 

 California. A careful sifting of the Dolichopodid fauna of 

 that State may reveal other allied species which will give a 

 clue to the natural affinities of the species here described. 

 Including a Hudson Bay species of Hercostomus described 

 by Loew and another described by Aldrich from St. Vin- 

 cent, West Indies, I append the following provisional table 

 of our North American species: — 



1. Postocular cilia black 2 



Postocular cilia white 3 



2. Legs black unicolor Loew. 



Legs yellow procerus, sp. nov. 



3. Antennae red latipes Ald. 



Antennae black inipudicus, sp. nov. 



8. Hercostomus procerus, sp. nov. 



Plate I, Figs. 9 and 10. 



Male. Length 4-5-5-5 mm.; length of wing 4-4.5 mm. Proboscis rather 

 small, piceous, with distinct hairs around its edge. Palpi small, covered 

 with gray dust. Face rather narrow, thickly covered with dull, ochre-yellow 

 dust. Antennae small, black; first joint with distinct hairs on its upper surface; 



