176 PROC. ENT. SOC. WASH., VOL. 23, NO. 8, NOVEMBER, 1921 



divisions. Before proceeding with the following short account 

 of the musculature of Pteronidea ribesii it is necessary to accur- 

 ately indicate the limits of each of the tergal areas. The four 

 areas are accordingly designated by the letters A, B,, C and D 

 (see Plate XIV, figs. 2 and 5) and are defined as follows: 



A the anterior of the three ornamented areas. In the abdomen it is the area 

 preceding that above the spiracle. 



B the area posterior of A. It is the second of the three oranamented areas 

 and the one which in the abdomen lies above the spiracle. (In some 

 sawfly larvae this area is large and subdivided. See Bl and B2 in draw- 

 ings of Cimbex americana. Plate XIV, fig. 7.) 



C the area posterior of B. It is the posterior of the three ornamented areas 

 and lies above the alar 1 area. (In certain sawfly larvae area C is large and 

 is subdivided, see Cl, C2, C3, in drawings of Neodiprion lecontei, plate 

 XIV, fig. 4.) 



D The area which is unarmed and posterior of C or anterior of A. (In certain 

 sawfly larvae this area is infolded and not visible as a distinct and sepa- 

 rate division of the segment, see drawing of Arge salicis, Plate XIV, fig. 8.) 



An idea of the musculature of Pteronidea ribesii may best be 

 had by an examination of the accompanying diagram (Plate 

 XIV, fig. 3) in which the principal muscles of the mesothorax, 

 metathorax, and first abdominal segment are pictured. It will' 

 be observed that all of the stronger infoldings marking areas 

 A, B, C and D are used to a certain extent as ridges for muscle 

 attachments for the majority of the large muscles. Both the 

 anterior and posterior margins of area A bear many muscles and 

 either margin more than both margins of all the other areas. 

 Furthermore all the long, longitudinal muscles, that (are seg- 

 mental) go from one segment to another attach only to the 

 margins of this area always uniting area A of one segment with 

 area A of the preceding and following segments. Thus we have 

 in each segment one area which bears on its anterior and pos- 

 terior margins the great majority of the muscle attachments, 

 and to either its anterior or posterior margin is attached at least 

 one end of all longitudinal muscles. This indicates area A as 

 either the first or last area of the segment. 



'In a paper recently published by the author ("Leconte's Sawfly, an Enemy 

 of Young Pines," Jour. Agri. Research, Vol. XX, No. 10, pp. 741-760, see foot- 

 note 1 on pages 742-3 and fig. F, plate 91) he adopts certain names for longi- 

 tudinal regions of the sawfly larval body and figures them. Under the tergum 

 he recognizes supraspiracular and spiracular regions (IV & V). Since the 

 spiracle does not always retain the same position on the body wall, i. e., within 

 the so called spiracular region, he proposes to substitute supraalar and alar 

 for the names supraspiracular and spiracular respectively and believes that in so 

 doing he increases the usefulness of the plan making it adaptable to other 

 groups where the spiracle is less fixed in its position than in the sawflies. 



