42 DIPTERA OF NORTH AMERICA. 



FAM. XLYII. PHYCODROMIDAE. 



Charact. Thorax, scutellum and abdomen flat ; pleurse excised above the 

 coxse. Front bristly ; border of the month hairy, with no distinct 

 vibrissse. Legs stout, tibise with spurs and each with an erect hair 

 or small bristle on the outside before the tip ; the first joint of the 

 posterior tarsi not abbreviated ; last joint of all tarsi enlarged, with 

 stout claws and long pulvilli. Neuration of the wings complete ; 

 auxiliary vein distinct in its whole length ; costa without bristles ; 

 basal cells not small. 



A certain resemblance with the Borboridce can by no means be 

 overlooked ; however, the Phycodromidce are readily distinguished 

 by the completeness of the auxiliary vein, the absence of the vibrissa? 

 so remarkable in those, by the first joint of the posterior tarsi not 

 being abbreviated, and by the increased size of the last joint of all 

 tarsi. They appear to have more true relation to the Helomyzidce, 

 but from these too they are sufficiently distinguished by the costa 

 of the wings having no bristles and the border of the mouth having 

 close hairs, but no real vibrissse. 



Of this family I have seen only one CffiLOPA captured in N. A. 

 It was remarkable by the exceedingly strong spines of its legs. 



FAM. XL VIII. HETEROXEURIDAE. 



Charact. Neuration of the wings complete, but the first longitudinal vein 

 rather short, and the auxiliary vein very much approximated to it ; 

 costa without bristles ; basal cells small. Front with long bristles ; 

 border of the mouth with a vibrissa at each side ; clypeus not deve- 

 loped ; palpi broad and proportionately large. Legs, and especially 

 the tarsi, slender ; middle and posterior tarsi with spurs ; all the 

 tibire without erect bristle on the exterior side before the tips ; claws 

 and pulvilli very small. 



I know five N. A. species of this family, four of which belong to 

 the genus HETERONEURA Meig. ; the fifth cannot be. conveniently 

 placed in any of the genera as yet established. 



