SMULYAN: NEW ENGLAND TENTHREDELLA. 393 
posterior angles on top of the narrow ridges (which it helps to 
form) between the mesoscutum and the true meso-postscutellum, 
to the base of the anterior wing. These continuations will be 
referred to as the mesoscutel transverse extensions in the descrip- 
tions. The mesoscutellum is, as a rule, more or less convex and 
often elevated (the degree of elevation depending upon the degree 
of convexity), and sometimes it is markedly convex and elevated 
[mellina (Norton)]. I have tried to indicate the progressive 
degree of convexity and elevation by the terms slightly convex, 
moderately convex, fairly strongly convex, etc. It often, too, shows 
a complete or partial, slight, median longitudinal carina. 
The post-tergite (Crampton, 1914; "postscutellum" of some 
authors) is the small and somewhat triangular plate which lies 
directly behind the mesoscutellum. It should be remarked in 
this connection that the application of the term post-scutellum 
to this sclerite is inadmissible, as the true meso-postscutellum is 
present though not superficially visible, being, as pointed out by 
Snodgrass (1910), invaginated and hidden within the insect body. 
This sclerite, like the mesoscutellum, shows as a rule a median 
longitudinal carina which is usually smooth, shiny and rather 
broad. 
The meso-epimcron is roughly plano-convex in outline. It 
lies immediately beneath the wings and above the episternum, 
and extends somewhat obliquel}^ from the mesocoxa to opposite 
the anterior portion of the base of the fore wing. The greater 
part of its surface is more or less depressed, and a slight, obliquely 
transverse swelling somewhat anterior to the middle, divides 
it into two unequal parts. 
The meso-episternum is rather large ; it lies immediately below 
the meso-epimeron, and like it extends from the base of the meso- 
coxa to opposite the anterior portion of the base of the anterior 
wing. On the ventral surface it fuses with the sternum. In 
this paper, however, the term is applied only to the lateral portion. 
The meso-episternum projects more or less away from the body, 
and is, as a rule, produced into a point about in the middle of 
the line of its greatest projection. I have tried to indicate the 
variability of the latter feature by such terms as slightly pointed, 
moderately pointed, fairly sharply pointed, etc., and blunt when no 
pointedness occurs. The lower limit of the meso-episternum is 
