174 THE CANADIAN ENTOMOLOGIST. 



as 2-4, 2 flat, as long as 3 + 4, which are simple and directed ob- 

 liquely outward Cepheu. 



Joint 3 shorter than 4; vein a a little before V2 ; cell III5 more nar- 

 rowed above ; HIj^ , acute ; labial palpi ordinary ; abdominal 

 fasciie, when present, continuous on segments 4-5, interrupted, re- 

 duced or wanting on 1-3 Centrias. 



3. Joint 3 distinctly shorter than 4 5. 



Joint 3 longer than 4, rarely a little shorter ' 4. 



4. Head and thorax without yellow ornaments, red; sutures, depressed 



and concealed portions black ; vein a interstitial with Vg ; apex of 

 hind tibijB with black curved bristles; joints 3-4 subequal; abdomen 

 red, a whitish spot on each side of segments 2-3, two subdiscal, 

 usually cuneate, spots on 4, and a transverse spot on 5 ; these 



marks sometimes wanting on 4, rarely on 2 and 5 P/ior. 



Head and thorax with yellow ornaments, usually black. .Holojiomada. 



5. Head and thorax without yellow ornaments ; vein a before 



Vj Noviada. 



Head and thorax with yellow ornaments 6. 



6. Vein rm usually (75%) wanting in one or both wings ; largely red ; 



segments 2-5 with yellow fascite, sometimes interrupted 



on 2 Heininomada. 



Vein rm present; mesonotum with four yellow lines; segments 1-6 

 with yellow bands Xanthidium. 



Males. 

 Mandibles bidentate Gnathias. 



Mandibles simple 1. 



1. Front coxae simple, rarely {JV. denticulata) with short, indistinct 



spines 3. 



Front coxae with pubescent spines; abdomen distinctly punctured. .2. 



2. Scape ordinary ; joint 3 longer than 4; vein a beyond, or interstitial 



with, V2 ; cell \\\^ subquadrate, HIn 2 obtuse ; segment 



7 bifid Cephen. 



Scape robust ; joint 4 = 5-1-6, 5 with a spine beneath ; flagellum usual- 

 ly yellow beneath, middle joints short, submoniliform, the last pro- 

 duced to a point Centrias. 



3. Segment 7 notched ; joint 3 shorter than 4 5. 



Segment 7 entire 4. 



