FAMILY TAClllMD.K TIIK TACIIIXIDS 425 



40. Second abdominal segment with dorsal bristles 46 



Second abdominal segment without dorsal bristles 41 



41. Sides of face diverging below; cheeks wider than length of thiril an- 



tenna! segment 42 



Sides of face slightly converging below; cheeks about as wide as 

 width of third antennal segment Xanthodexia Wulp 



42. Face strongly carinate 44 



Face at most weakly carinate 43 



43. Proboscis decidedly longer than the head-height. . . Prosenoides Townsend 

 Proboscis shorter than the head-height (118, 122) Billsea Desvoidy 



44. Antennae not nearly reaching the vibrissas 45 



Antennae reaching almost to the vibrissa Theresiopsis Townsend 



45. Facial carina not convex in profile 48 



Facial carina convex in profile Opsotheresia Townsend 



46. Facial carina strong and prominent 51 



Facial carina weak, obsolete or nearly so 47 



47. Apical cell ending in or near the wing-tip. 



Stomatodexia Brauer & Bergenstamni 

 Apical cell ending far before the wing-tip 48 



48. Antennae reaching about half way to the oral mSrgin. 



Phalacrophyto Townsend 

 Antennae reaching more than half way to the oral margin 49 



49. Abdomen broadly oval; larger, more or less castaneous species. 



Theresia Desvoidy 

 Abdomen narrower; smaller, non-castaneous 50 



50. Second abdominal segment without strong marginals. 



Paratheresia Townsend 

 Second abdominal segment with a pair of strong marginals. 



*Eutheresia Towmsend 



51. Second abdominal segment with only one pair of marginals, or they 



are not spine-like 52 



Second abdominal segment with three or more pairs of marginal 

 spines; lai'ge, robust species Chaefogyne Brauer & Bergenstamm 



52. Claws short and thick basally, bent at almost a right angle at their 



middle; parafacials with inconspicuous hairs. 



Myiomima Brauer & Bergenstamm 

 Claws normal, moderately curved apically (118, 122) . . .Billaea Desvoidy 



53. Infrasquamal setulse absent, abdomen always with bristles, at least 



on the apical segments 159 



Infrasquamal setul?e present or the abdomen without well-developed 

 bristles 54 



54. Eyes thickly haired 55 



Eyes bare or with inconspicuous, short, sparse hair 84 



55. Parafacials with hairs or bristles on at least the upper half 56 



Parafacials bare or with only a few hairs below the f rentals 65 



* Cuiran, 1929, Can. Ent., Ixi, p. 33. 



