THE SAWFLIES OF BOULDER COUNTY, COLORADO IOI 



(15) C. cerasi (Linnaeus). This is the common cherry and pear slug. The adult 

 may easily be recognized by the transverse radius nearly interstitial with the third trans- 

 verse cubitus. For a figure of the adult and larvae, see Marlatt, 1897, p. 1. 



Subfamily NEMATINAE 



Prepectus present; metaepimeron with a small curved dorsal plate which usually 

 projects laterally beyond the lower part of the small plate ; the third pleural suture strongly 

 curved; basal vein and first recurrent vein strongly divergent, the first recurrent vein 

 being much shorter than the basal; basal vein joining the costa remote from the origin of the 

 cubitus; anal cell contracted in the middle or petiolate; transverse radius present or 

 absent, but most usually absent, and often when present it may not be constant in an 

 individual (i.e., the transverse radius may be present in one wing and absent in the other). 



Tribe Hemichroini 

 Anal cell of the fore wings contracted and closed in the middle. 



Genus HEMICHROA Stephens 

 Malar space long; head and thorax shining, not coarsely sculptured; transverse 

 radius present; second cubital cell receiving both recurrent veins; tarsal claws cleft. 



(16) H. americana (Provancher). Male: Length 5 mm. Black; legs below coxae 

 ferruginous, tibiae often paler; wings dusky hyaline, venation dark brown. Provancher's 

 type has not been studied and this may not be his species. 



Males collected on Salix and Alnus in May, 1907, Lower Boulder Canyon (S. A. 

 Rohwer). 



Tribe Nematini 



Anal cell of the fore wings petiolate. 



Many of the insects belonging to this tribe feed in the larval stage on species of the 

 Salicaceae, and as a number of species of Populus and many species of Salix occur in 

 Boulder County, many more species may be found in the county. There are, however, 

 species of this tribe which feed on other plants, such as Pteronidea ribesii, which feeds on 

 currants, Pachyncmalus extensicornis which lives on wheat, Nematus erichsonii 

 which feeds on larch, Prisliphora idiota which feeds on cranberries, etc. This is another 

 Holarctic group of northern distribution, the adults of which appear in the spring or 

 early summer. In this tribe are leaf or stem gall-makers, and solitary or gregarious 

 external feeders. Very little indeed is known about the western larvae, and anyone will 

 do science a good turn who records careful observations on the western larvae. 



The genera belonging to this tribe are rather numerous, but only three have so far 

 been recorded from the limited area here treated. The species in this group are often 

 superficially identical, although separated by valuable head characters, so in this group, 

 more than any other, must one master the characters used in classification before careful 

 identification can be made. 



Genus EUURA Newman 



Transverse radius wanting; second transverse cubitus wanting; clypeus emarginate; 

 pentagonal area present or wanting; claws cleft or with a large subapical tooth. 



