FAiMILY DOLICHOPID.E — THE LONG-HEADED FLIES 221 



Mesonotum without such depression, usually with a slight, transverse 

 depression 42 



35. Acrostical setulse present, at least at the anterior edge of the thorax. 36 

 Acrostical setulae absent Micromorphus Mik 



36. Third and fourth veins almost parallel beyond the crossvein 37 



Third and fourth veins converging before the apex (52). 



*NeuriRona Rondani 



37. Acrostical setulae present only on the anterior margin of the meso- 



notum (60) Xanthochlorus Lcew 



Acrostical setulae extending at least to the suture 38 



38. Sixth (anal) vein present 39 



Sixth ( anal ) vein absent 40 



39. Hair and bristles wholly yellow (11) Chrysotimus Lcew 



Hair and bristles not yellow (52) *Neurigona Rondani 



40. Arista apical (36) 41 



Arista sub-apical; third antennal segment pointed (62) . .jAchalcus Lcew 



41. Pleura metallic (6, 7) Collinellula Aldrich 



Pleura yellow; third antennal segment rounded apically (4, 36). 



fXanthina Aldrich 



42. Fourth vein ending well before the tip of the wing; posterior cross- 



vein very oblique ( 19 ) 43 



Fourth vein ending but little before the tip of the wing, usually in or 

 slightly behind it 44 



43. Dorsocentral bristles strong (19) Plagioneurus Lcew 



Dorsocentral bristles hair-like CEdematopus Van Duzee 



44. Posterior crossvein situated less than its own length from the wing 



margin along the fifth vein, the basal segment of the posterior tarsi 



longer than the second (43) 45 



Posterior crossvein much shorter than the ultimate section of the 

 fifth vein, or the first segment of the posterior tarsi decidedly 

 shorter than the second (9) 49 



45. Pteropleura haired in front of the posterior spiracle 46 



Pteropleura bare 47 



46. First antennal segment with stout setulae below (72)..MeIanderia Aldrich 

 First antennal segment bare below (Hydrophorus pt) (80). 



Millardia, n. g. 



47. Pteropleura produced to form a mammiform projection in front of 



the posterior spiracle (27, 28) JScellus Lcew 



Pteropleura plain 48 



48. Middle of the propleura haii-ed; third antennal segment subrectangu- 



lar, the arista dorsal (26, 43, 56, 78) §Hydrophorus Fallen 



* Van Duzee, 1913, Ann. Ent. Soc. Amer., vi. pp. 22-61. 



t The only difference in these two genera appears to be in the shape of the third antennal 

 segment. They should probably be united. 



± Greene, 1924, Proc. U. S. N. M., Ixv, Art. 16. 

 § Van Duzee, 1926. Pan.-Pac. Ent., iii, p. o. 



