CEEATOMYIELLA AND PAEADIDYMA REINHAED 19 



dorsocentral, 3, 3; humeral, 2; posthnmeral, 1; presutiiral, 1; noto- 

 pleural, 2 ; intraalar, 2 ; supraalar, 2 ; postalar, 2 ; hypopleural, 4 or 

 5; pteropleiiral, 1 (^mall) ; sternopleural, 2, 1 (lower anterior one 

 small). Scutellum with two lateral, one decussate apical and a 

 small discal pair. Postscutellum normally developed; infrasquamal 

 hairs present. 



Abdomen without discal bristles on intermediate segments. 



Legs rather long and slender, claws and pulvilli elongate in male. 



Wing3 with first vein bare; third bristled nearly to small cross 

 vein. Costal spine developed. Last section of fifth vein less than 

 half as long as the preceding one. Hind cross vein oblique to fourth, 

 which it joins a little nearer bend than small cross vein. Apical 

 cell narrowly open, reaching costa well before extreme tip of wing. 



KEY TO SPECIES OF PABADIDYMA 

 MALES 



1. Apical cell closed and petiolate 2. 



Apical cell oi>en 4. 



2. Mesonotum gray pollinose, the black stripes couspicuous and 



usually fused into a single liroad pair, wliich extends to base 



of scutellum 3. 



Mesonotum subshining, at most lightly dusted with pollen, the 

 black stripes poorly defined or entirely obliterated behind 

 suture : third antennal segment ordinary ; arista thickened 

 on basal two-fifths (Indiana, Illinois, Maryland, Virginia). 



(23) petiolata, new species. 



3. Last three abdominal segments: with silvery bands on basal 



third, the remainder of these segments including the first 

 shining black; third antennal segment entirely black 



(United States, widespread) (22) singularis (Townsend). 



Pollen on abdomen not in defined basal bands, first segment 

 conspicuously pollinose on the sides above, the second with 

 pollen extending to hind margin ; base of third antennal 

 segment yellow to insertion of arista (Brazil). 



(21) brasiliana, new species. 



4. Last section of fifth vein one-half the length of preceding section 5. 



Last section of fifth vein distinctly less than one-half as long as 



preceding section 8. 



5. Acrostichals only two pairs well developed before suture 6. 



Three pairs of strong presutural acrostichal bristles; palpi 



brownish ; abdomen almost wholly covei-ed with gray pollen ; 

 fourth segment bearing a row of strong discal bristles (New 

 Mexico) (8) neomexicana, new species. 



6. Second antennal segment distinctly longer than first 7. 



Ba.s.il segments of antennae subequal in length; pollen on 



thorax and abdomen tinged with brown; postsutural acros- 

 tichals one pair; calypters tawny (Mexico)^- (9) derelicta, new species. 



7. Last three abdominal segments with defined silvery bands 



on basal fourth, the remainder of these segments including 

 the first shining black; mesonotum thinly pollinose, sub- 

 shining; palpi pale yellow; two sternopleural bristles (Utah). 



(11) retracta, new species. 



