NORTH AMERICAN HYMENOPTERA. 225 



54. — Cheeks not spinose beneath, unarmed ; convexities of enclosure of middle 

 segment smooth, polished ; hind tibise yellow at base only ; clypeus and 



scape posteriorly, black erraiiN. 



Cheeks with a strong spine beneath ; convexities of enclosure of middle seg 

 ment distinctly striated ; hind tibite except a blotch within, clypeus and 



scape entirely, yellow arniaticeps. 



55. — Fore tarsi not flattened or distorted 56. 



Fore tarsi greatly flattened, or the first joint twisted or distorted 63. 



56. — Ultimate dorsal abdominal segment distinctly more strongly punctured than 



the penultimate .57. 



Ultimate dorsal abdominal segment not, or scarcely, more strongly punctured 



than the penultimate 60 



57. — Posterior face of middle segment transversely rugose 58. 



Posterior face of middle segment rugose at apex only (clypeus spotted with 



yellow; inaciiliclypetis. 



58. — Clypeus and greater part of scape, prosteruum and fore coxse and trochan- 

 ters, black 59. 



Clypeus and scape entirely, prosternum, fore coxte and trochantei's, bright 



yellow pictipes. 



59. — " At the base of propodeum (middle segment) is a row of minute fosste." 



iiiiiiiinus. 



Base of middle segment with a wide, somewhat triangular, excavated area, 



which is longitudinally ridged ; pronotum very strongly crested, angular 



at sides- siiIcum (?). 



60. — -Thorax without yellow spota 61. 



Prothorax and scutellum yellow impressifroiis. 



61. — Enclosure of metathorax with two large, smooth areas 62. 



Enclosure of metathorax with two small, indistinct, smooth areas. 



cinctipes. 

 62. — Legs entirely black ; anterior margin of clypeus rounded out in the middle. 



aler. 

 Greater part of four anterior legs reddish ; hind tarsi dark testaceous. 



nigrieoriiis. 

 63. — Thorax not maculated with yellow ; basal joint of fore tarsi twisted. 



tar»«alis. 

 Prothorax, tubercles and scutellum marked with yellow; basal joint of fore 



tarsi greatly flattened, but not twisted planipes. 



64. — Episternum mesopleuralis ridged anteriorly ; head and thorax coarsely punc- 

 tured ; petiole scarcely nodose at apex (antennae simple, not dentate). 



aKperatus. 

 Episternum mesopleuralis not ridged anteriorly ; head and thorax finely 



punctured 65. 



65. — Antennge not dentate or lobate beneath, sim])le : petiole of abdomen shorter 

 than the following segment; coxse black (scape and legs in part yellow; 



otherwise black) occidentalis. 



Antennae more or less dentate or laminate beneath ; petiole of abdomen 



longer than the following segment ; coxae yellow 66. 



66. — Abdomen black, not banded with reddish ; four anterior legs more or less 



black; first joint of medial tarsi laminate internally, .peclicellatujii. 



Abdomen black, the third segment banded with reddish ; four anterior legs 



entirely yellow; first joint of medial tarsi not laminate -rufogsister. 



TRANS. AM. ENT. SOG. XXII. (29) JUNE, 1895. 



