406 HYMENOPTEKA. 



sion bears short thick keels, this being also the case on the opposite depression on the 

 mesopleurae). The breast is furrowed deeply in the centre, the furrow bearing short 

 thick keels. Abdomen about one half longer than the thorax. Petiole excavated at 

 the base, longer than the second segment ; a deep, wide, rather long depression on 

 either side on the basal three fourths, the depression narrowest at the base, the central 

 part of the base margined at the edges where it bounds the depression. Second segment 

 depressed at the base and down the sides, with a broad and deep transverse depression 

 on either side in the centre, the depression separated only by a narrow partition in the 

 middle ; third segment with a broad and deep excavation at the base ; fourth segment 

 with a moderately broad and deep transverse depression (narrower and shallower than 

 that on the second segment) on either side in the middle. The abdomen bears a short 

 black pubescence. Areolet complete, longer than broad. 



10. Microdus albitarsis. 



Ferrugineus, capite, antennis, prosterno pedibusque nigris, tarsis albis ; alis fuliginosis. 

 Long. 13 millim. 



Eab. Mexico {Salle). 



Head shining, microscopically pilose in front ; face punctured ; frontal depression 

 moderately deep, continuous. Thorax shining, the mesonotum finely punctured, the 

 metanotum strongly rugosely reticulated. Petiole with the basal half raised in the 

 centre, the raised part becoming gradually narrower from the base to the apex. Second 

 segment with a stout keel down the sides ; the furrows as in M . basimacula. 



2. Suturiform articulation distinct, striated, narrow ; base of the abdomen 

 more or less longitudinally striated. 



1. Outer nervure of the areolet obsolete; thorax and the base of the 



abdomen ferruginous melanocephalus. 



2. Areolet shortly petiolate ; thorax and the base of the abdomen black . montivagus. 



/^ll. Microdus melanocephalus. 



Ferrugineus, capite, antennis, basi metanoti pedibusque nigris, geniculis, coxis posticis supra femoribusque 



postieis runs ; alis fuscis. tf . 

 Long. 6*5 millim. 



Eab. Mexico, Northern Sonora (Morrison). 



Antennae rather slender, not densely pilose. Head impunctate, shining ; face sparsely 

 covered with pale hair; a large depression over each antenna. Thorax shining, the 

 metanotum rather strongly punctured (especially at the base) and indistinctly keeled ; 

 the sides covered with rather long white hair. Petiole and the base of the second 

 segment slightly longitudinally striated. Second segment with a transverse striated 



