No. 1774. 



THORAX OF HYAIEN0PTERA—8N0DGRA88. 



49 



The posterior part of the prosternum frequently bears a long internal 

 spine projecting posteriorly, hence the name "spinisternum" of 

 Cramp ton. 



Wings. — In immature stages the wings appear to be hollow expan- 

 sions of the back plates of the mesothorax and metathorax. In 

 adults the upper surface of each is continuous by membrane with 

 the edge of the notum and the lower surface with that of the pleurum. 

 Each is more firmly hinged to the wing processes of the notum by 

 two small axillary sclerites, and is pivoted upon the wing process of 

 the pleurum by another. 



Wing membrane. — The appressed dorsal and ventral walls of the 

 original wing sac, forming the cells between the chitinous veins and 

 the thin axillary memlrane between the axillaries. The second is 

 nearly always bordered 

 posteriorly by a con- 

 spicuous ligament-like 

 thickening, the axillary 

 cord (figs. 1, 8, and 10, 

 AxC) arising typically 

 from the posterior an- 

 gles of the notum at 

 the outer ends of the 

 posterior reduplication 

 (figs. 1, 2, and 3, AxG 

 and Rd) . Sometimes 

 the axillary membrane 

 forms a large lobe or a 

 pair of lobes, called the 

 alula, at the posterior 

 angle of the wing base. 

 On its anterior edge is a 

 hairy pad, the tegula (Tg), which, in the front wing, is sometimes 

 developed into a large scale overlapping the root of the wing. 



Wing veins.— The writer adopts the Comstock-Needham (1898) 

 system of wing venation and nomenclature for morphological pur- 

 poses, but he does not advocate its use by systematists for descriptive 

 purposes. A vein that is evidently a compound of several original 

 veins must, according to this system, be named as the sum of all its 

 components. Thus results such appellations as Sc + Ri- M, or Cui + 

 Cu2 + M^ + lstA-\-2dA+3dA for names of veins in the Hymenopteran 

 wing. Combinations of this sort are certainly too cumbrous to be 

 practical— a systematist should not be required to use such complex 

 terms when he wants to mention a particular vein of the wing. 

 Hence, while this system may be used to show the morphology of 

 Proc.N.M.vol.39— 10 4 



Fig. 8.— Theoretical diagram of a wing-bearing tergum and 



BASE OF wing: 1A , FIRST ANAL VEIN; A NP, ANTERIOR NOTAL 



WING process; anr, line of anterior ventral notal ridge; 

 lAx, ZAx, 3 Ax, 4Ax, first, second, third, and fourth axil- 

 laries of wing base; AxC, axillary cord; C, costa; Cu, 

 cubitus; M, media; m, median plates of wing base; N, 

 notum; PiV,PosTNOTUM; PNP, posterior notal wing proc- 

 ess; pnr, line of posterior ventral notal ridge; Pph, 

 postphragma; R, radius; Sc, subcosta; Tg, tegula; mr, 



UNE OF median VENTRAL V-SHAPED NOTAL RIDGE. 



