CERATOMYIELLA AND PARADIDYMA REINHAED 37 



In the material examined I have noted but one specimen (female) 

 having the first posterior cell closed and short petiolate. In singu- 

 laris the first posterior cell is invariably closed and usually short 

 petiolate. Other differences may be noted in the present species: 

 Four narrow thoracic stripes; fourth abdominal segment with 

 discals above in male; outer verticals present in female. 



(20) PARADroYMA VALIDINERVIS (Van der Wulp) 



Didyma validinervis Van der WrrLP, Biologia Centrali-Americaua, Diptera, 



vol. 2, p. 164, 1890. 

 Paradidyma validinervis Braxjer and Beirgbnstamm, Die Zweifliigler des 



kaiserlichen Museums zu Wien, uo. 5, p. 404, 1891; no. 6, p. 127, 1893. 



Besides the characters mentioned in the generic description, the 

 type species has the following additional characters: 



Male. — Front narrowed before vertex, at narrowest part 0.22 of 

 the head width in one specimen; parafrontals covered with dense 

 gray pollen to vertex, sparsely clothed with hairs outside of frontal 

 rows ; median stripe reddish brown, at middle wider than one para- 

 frontal; inner verticals developed; frontals ordinary in size, the 

 uppermost bristle subreclinate and hardly stouter than the preceding 

 one; parafacials densely gray pollinose, bare below level of arista 

 outside of the main bristles, which increase in size downward in the 

 row; antennae black, third segment about four times the length of 

 second; arista pubescent, thickened about on proximal half; palpi 

 dark brown ; cheek clothed with black hairs on lower margin, about 

 two-fifths the eye height; eyes hairy. 



Thorax black, gray pollinose ; mesonotum marked with four black 

 stripes, outer pair interrupted at suture; scutellum black, thinly 

 gray pollinose; calypters whitish, the hind lobe translucent and 

 with a slight brownish tinge. 



Abdomen black; segments two to four shining beyond the basal 

 silvery band, only the second showing thin pollen more extensively 

 in a flat rear view; basal segments each with a pair of median mar- 

 ginals; third bearing a marginal row of six, large; fourth with a 

 row of six discals, which are slightly stouter than the marginals; 

 genital segments black. 



Legs black; claws and pulvilli elongate. 



Wings grayish hyaline; first vein bare, third setulose almost to 

 small cross vein; apical cell narrowly open; last section of fifth 

 vein less than half as long as preceding section ; costal spine devel- 

 oped. 



Length. — 7 mm. 



Reinarhs. — Redescribed from one cotype male specimen in the 

 United States National Museum from Guerrero, Mexico. I have 

 not seen any specimens of the female. 



