E. T. CRESSON, JR. 41 



normally coalesces with the first near its extremity, and the 

 discal and second basal cells are rarely separated. 



The species seem to merge nicely with some Drosophilids, but 

 the latter have a more or less distinct vibrissac. On the other 

 hand some seem to simulate the Borboridae, but the short basal 

 joint of the hind tarsi will distinguish the members of that family. 

 In the Geomyzidae there is a distinct vibrissal angle and bristle. 

 With the exception of a few genera, for instance — Brachydeutera, 

 Ochthera, Psilephydra, Canace and Planinasus, the species are 

 very constant, with the above family characteristics well em- 

 phasized. The genus Planinasus is probably marginal in its 

 position, possibly a representative of another family. 



Analytical Table of the Genera occurring or likely to occur in 

 Costa Rica 



1. Discal and second basal cells separated by a cross vein; cheeks with one or 



more upcurved bristles. (Maritime species. Neotropical ?) . . . Canace 



Discal and second basal cells not separated; cheeks with or without a 



ventro-proclinate bristle 2 



2. Fore femora greatly dilated; third and fom-th veins converging . . Ochthera 

 Fore femora not thickened; third and fourth veins parallel or diverging. . .3 



3. Face below broad, prominent, setulose; mouth large, vaulted; frontal 



bristles curving laterally over eyes 4 



Face broad, prominent, convex and swollen, not setulose, with no distinct 



bristles or orbital area; mouth rather narrow; no distinct frontal bristles; 



antennae small with very long, nearly bare arista PsUephydra 



Face not setulose medianly, with only a series of one or more bristles on 



each side 6 



4. Costa extending to fourth vein 5 



Costa not reaching fourth vein Scatophila 



5. Claws generally long, nearly straight; pulvilli minute Ephydra 



Claws small, curved; pulvilli well developed Scatella 



6. Middle tibiae with two or more erect extensor bristles 7 



Without such bristles 8 



7. Costa extending to fourth vein Paralimna 



Costa not attaining fourth vein Notiphila 



8. One or more distinct dorso-central bristles (exclusive of the prescutellar 



pair) 9 



No dorso-central bristles 12 



9. Eyes pilose; facial bristles hair-like 10 



Eyes bare; facial bristles strong 11 



10. Frontal bristles absent; face prominent below Nostima 



Frontal bristles present; face not produced Hydrellla 



TRANS. AM. ENT. SOC, XLIV. 



