Q PROCEEDINGS OF THE NATIONAL MUSEUM vol. 70 



KEY TO SPECIES OF OPSODEXIA 



1. ^bdomen yellow bicolor Coquillett. 



Abdomen black 2. 



2. Legs yellow ; abdomen without discals ; wings hyaline. 



abdominalis, new species. 

 Legs black ; abdomen with discals ; wings distinctly inf uscated. 



cruciata, new species. 



OPSODEXIA ABDOMINALIS, new species 



Male. — Front at narrowest part 0.11 of head width; parafrontals 

 silvery, narrowed before vertex and widening rapidly below, with 

 a few short inconspicuous hairs outside the frontal rows; median 

 btripe blackish, considerably broader than the parafrontal at base of 

 antennae, greatly narrowed posteriorly but distinctly wider than 

 the anterior ocellus; frontals in two diverging rows of six or seven 

 rather short bristles, stopping at base of antennae, the uppermost 

 pair hairlike and situated some distance before the ocellar triangle, 

 which bears a pair of strong, proclinate, nondivergent bristles mid- 

 way between the anterior and posterior ocelli, several long bristles 

 present on posterior margin of triangle; orbitals none; inner ver- 

 ticals w^ell developed, curving posteriorly; parafacials strongly 

 divergent below, shining silvery, with one or two short hairs on 

 upper extremity, about equal to width of third antennal joint; facial 

 depression shallow, without a carina, densely gray pollinose on red- 

 dish background; ridges flattened below, becoming sharp and more 

 prominent above, with one strong and several weaker bristles above 

 vibrissae, which are situated on level with oral margin; antennae 

 three-fourths the length of face, basal joints yellow, third joint 

 blackish, pubescent, about twice the length of second joint; arista 

 yellowish beyond the briefly thickened black base, with moderately 

 long hair on upper side extending more than halfway to tip, and a 

 few short inconspicuous hairs beneath near the base, penultimate 

 joint longer than broad; proboscis short, fleshy; palpi black, smaller 

 than usual, hardly thickened apically; cheeks one-fourth the eye 

 height, very thinly gray pollinose on red ground color; occiput 

 somewhat swollen below, covered with a thin layer of gra}^ pollen 

 and bearing only short black bristly hairs arranged in irregular rows 

 above ; eyes bare. 



Thorax and scutellum black, with rather uniform gray pollen 

 w^hich appears denser when viewed from the front ; mesonotum, ex- 

 cept immediately in front of transverse suture, subshining in rear 

 view, without any distinct vittae. Chaetotaxy: Humeral 2; post- 

 humeral 3; presutural 1; notopleural 2; pteropleural 0; acrosti- 

 chal 0, 1 (in transverse row with posterior dorsocentrals) ; dorso- 

 central 3, 3 (anterior slightly outside the row) ; intraalar 3 (anterior 



