NO. O INSECT ABDOMEN SNODGRASS 123 



elements in the basal mechanism of the sting, but their true seg- 

 mental relations are attested by the muscles that connect them with 

 the spiracular plates of the eighth tergum (fig. 46 D, E, 14). 



The ninth segment has lost all resemblance to a segmental annulus. 

 The median part of its dorsum is indistinguishable from the mem- 

 branous wall of the proctiger (fig. 40, Ptgr) ; the lateral parts, how- 

 ever, form a pair of large quadrate plates (I XT), which are im- 

 portant elements of the sting mechanism. Each is overlapped dor- 

 sally by the spiracular plate of the eighth dorsum. The pleural parts 

 of the ninth segment are represented by the oblong second valvifers 

 {2Vlf), which are largely overlapped by the quadrate tergal plates. 

 The ventral region of the segment, lying between the valvifers, is 

 membranous and is ordinarily arched upward (fig. 45 A, IXV), 

 forming beneath it a deep concavity thickly clothed with slender 

 spinelike hairs, in which is lodged the bulbous basal part of the sting. 



The proctiger, when fully protruded (fig. 40, Ptgr), is a mem- 

 branous cone with the anal opening {An) at its distal end. The 

 ventral wall of the proctiger contains a weakly sclerotized area. 



Structure of the sting. — The stinging apparatus of the bee in- 

 volves nearly all the parts that are invaginated within the seventh 

 abdominal segment (fig. 40). These parts include the spiracle-bearing 

 plates of the eighth tergum (Lsp) , the lateral plates of the ninth 

 tergum (IXT), the first and second valvifers {iVlf, 2Vlf), and the 

 valvulae, which form the rami and shaft of the sting (Stng). The 

 proctiger (Ptgr) , because of its natural connections, is intimately as- 

 sociated with the stinging mechanism. The structure of the sting of 

 the honey bee has been described by Sollmann (1863), Kraepelin 

 (1873), Cheshire (1886), Snodgrass (1910, 1925, 1933), Zander 

 (191 1), Betts (1923), Leuenberger (1928, 1929), and various other 

 writers. The well-known facts are repeated here in order to show 

 the homologies between the parts of the sting and those of the ovi- 

 positor of other insects, and also that their description may serve as 

 as basis for a closer study of the musculature and a better under- 

 standing of the mechanism of the sting. 



Students of bee anatomy have adopted special names for the parts 

 of the sting apparatus, which are convenient to use for descriptive pur- 

 poses. The lateral sclerites of the eighth tergum bearing the spiracles 

 are known as the spiracular plates (laminae spiracitlares) ; the lateral 

 sclerites of the ninth tergum are the quadrate plates, the first valvifers 

 are the triangular plates (Winkel of German writers), and the second 

 valvifers the oblong plates. The first valvulae are the darts, or lancets 

 (Stechborstcn). The structure formed by the united second valvulae 



