456 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.4?.. 



45. Mesopleura with one bristle noticeably longer and stronger than the others 46. 



Mesopleural bristles of nearly equal lengths, no one bristle particularly long and 



strong 47. 



46. One very long, and strong, backwardly-directed bristle; male third antennal joint 



half as large as eye; costa to two-fifths of wing length arizonensis, p. 478. 



One bristle noticeably longer than the others but not remarkably long nor strong, 

 male third antennal joint of normal size; costa to about middle of wing. 



monticola, p. 479. 



47. Costa to near the middle of wing 48. 



Costa at most two-fifths of wing length 49. 



48. Small brownish species (1^ mm. at most); first costal division about one and one- 



half times as long as other two together, fringe long franconiensis, p. 479. 



First costal division at least twice as long as other two together; species about 

 2J mm. in size dubitata, p. 480. 



49. Costa very short, about one-third the wing length, frons longer than broad, dis- 



tinctly shining, fourth and fifth wing veins divergent from base to tip. 



divergens, p. 480. 



Costa to two-fifths the wing length; frons about as broad as long, gray dusted 



anteriorly, fourth and fifth wing veins parallel on basal half 50. 



50. First costal division about one and one-half times as long as other two together. 



atomella, p. 481. 

 First costal division distinctly more than twice as long as other two together. 



subatomella, p. 481. 



51. Halteres black or brown 52. 



Halteres yellow 58. 



52. Costal fringe very short 53. 



Costal fringe long 54. 



53. Costa short of wing middle, first division distinctly longer than other two together; 



hind tibial setulae indistinct, brownish black species .fungicola, p. 485. 



Costa to middle of wing, first division only as long as other two together; hind 

 tibial setulse distinct; black species. 



a. Two pairs of post-antennal bristles present .furtiva, p. 486. 



6. Only one pair of post-antennal bristles present bicqlorata, p. 486. 



54. Costa to middle of wing 55. 



Costa short of middle of wing 56. 



55. Costa distinctly swollen, halteres brown conspicualis, p. 487. 



Costa normal, halteres black .' inornata, p. 488. 



56. Frons longer than broad, upper post-antennal bristles separated by more than one- 



third the breadth of frons, lower pair by about one-fourth; palpi yellow. 



borealis, p. 488. 



Frons broader than long, upper post-antennal bristles separated by about one- 



fom-th the breadth of frons, lower pair but little closer; palpi black 57. 



57. Halteres brown, abdomen with short hairs, longer and quite prominent on ventral 



surface at near tip rusticata, p. 489. 



Halteres deep black, abdomen nearly bare, the ventral sm-face near tip with only 

 a few rather short hairs perplexa, p. 489. 



58. Costa to distinctly beyond middle (see smii^n Brues) 59. 



Costa to middle, or short of it 62. 



59. Hind tibial setulas distinct and not particularly numerous 60. 



Hind tibial setulee' hair-like and very numerous or indiscernible 61. 



60. Small glossy brownish species (1-1 J mm.); both pairs of post-antennal bristles 



present chaetoneura, p. 490. 



Larger black species (3^ mm.); only one distinct pair of post-antennal bristles. 



infumata, p. 490. 



