ART. 1. NORTH AMERICAN SAWFLIES ROHWER. 25 



Distribution. — The species of this genus are distributed throughout 

 the Palaearctic Region; one is known from the northern Oriental 

 Region; and several occur in Nearctic Region, where they are con- 

 fined almost entirely to the eastern part of the Transition and Cana- 

 dian Zones. 



Sjyeci-fiG Characters. — In the adults the shape of the sheath, the 

 exact dentation of the lancet plates, the character of the frontal crest, 

 and the presence or absence of foveae in the postocellar area offer the 

 best structural characters for separating the species. The color of 

 the legs, even to the number of tarsal joints which are black or in- 

 fuscated, is very useful in separating the species, and for all of the 

 species here treated it is found to be surprisingly constant. 



KEY TO THE ADULTS. 



The species petrinus (Cockerell) and infuscatus (MacGillivray) are omittetl 

 from the following key (see also footnote 1) : 



1. Females 2 



Males 11 



2. Lower walls of ocellar basin strong, keel-like, sharply broken by the middle 



fovea, the lateral walls sharply defined, linelike; postocellar area sepa- 

 rated by a median furrow; wings with a dusky band below the stigma; 



antennae long, sharply tapering; trochanters white crataegi Rohwer. 



Lower walls of occellar basin not especially strong, rounded, not or only 

 feebly broken by the middle fovea ; the lateral walls obsolete or poorly 

 defined ; postocellar area convex, with, at most, a fovea anteriorly 3 



3. Postocellar area without a fovea near the middle of the anterior margin 4 



Postocellar area with a fovea near the middle of the anterior margin 8 



4. Distinct large, somewhat triangular-shaped depression in front of the an- 



terior ocellus ; hind tarsi and all of the trochanters black betulae Rohwer. 



No large or triangular-shaped depression in front of the anterior ocellus 5 



5. Recurrentella distinctly postfurcal rubivorus Rohwer. 



Recurrentella antef ureal G 



6. Wings before of the anterior margin of the stigma, brownish ; trochanters 



and hind tarsi brownish black salicivorus Rohwer. 



Wings uniformly hyaline; trochanters and hind tarsi white 7 



7. Middle fovea deep, large solitaris (Dyar). 



Middle fovea practically obsolete montanus Rohwer. 



8. Trochanters black ; ocellar basin entirely obsolete ; frontal crest unbroken ; 



sheath oblique above, obtusely rounded apically, tapering to a broad base ; 



antennae long, slender, sharply tapering apically rubi Rohwer. 



Trochanters white; at least the lower wall of the ocellar basin distinctly 

 present 9 



9. Frontal crest not broken medianly ; antennae slightly shorter and not strongly 



tapering; wings brownish basally pruni Rohwer, 



Frontal crest broken medianly ; antennae slightly longer and sharply taper- 

 ing apically 10 



10. Wings strongly brownish basally virginianus Rohwer. 



Wings uniformly hyaline plesius Rohwer. 



11, Postocellar area with a small distinct fovea at the anterior middle ; tro- 



chanters white; hind tarsi mostly white 12 



Postocellar area without a fovea at the anterior middle; trochanters and 

 hind tarsi brownish 13 



