NO. G INSECT ABDOMEN SNODGRASS I39 



of the wounH by the shaft after the tip of the latter has once been 

 inserted ; and incidentally these movements accomplish also the injec- 

 tion of the poison by motion of the valves of the lancets in the poison 

 chamber of the bulb. The skeletal parts in the basal apparatus con- 

 cerned with the movement of the lancets are the first and second valvi- 

 f ers and the quadrate plates ; the motor elements are the anterior and 

 posterior muscles of the second valvifers. 



It will be unnecessary to review the opinions of other writers on 

 the working of the mechanism that moves the stylets, since all investi- 

 gators except Sollmann (1863) have wrongly attributed the attach- 

 ment of the dorsal group of fibers of the anterior second valvifer 

 muscles (fig. 47 A, lya) to the first valvifers, while Sollmann on his 

 part, besides committing various other inaccuracies, believed the ven- 

 tral group of fibers (lyb) to be attached on the first valvifer. Hence, 

 all descriptions of the sting mechanism contain the error of attempting 

 to explain the movements of the lancets as caused by muscles inserted 

 on the first valvifers. Notwithstanding this mistake, Kraepelin (1873) 

 is not far wrong in his account of the working of the sting, inasmuch 

 as he deduces the correct movements of the lancets from his concept 

 of the mechanism. 



The only muscle inserted on the first valvifer (triangular plate) 

 in the bee, as already shown, is the slender muscle from the lower 

 margin of the spiracular plate of the eighth segment (fig. 46 D, E. 

 14) ; but this muscle is attached on the valvifer so close to the posterior 

 end of the latter, and has such a weak support on the spiracular 

 plate, that it seems probable its chief function is to maintain a proper 

 relation between those two sclerites. The principal muscles that ac- 

 complish the movements of the lancets in the bee are undoubtedly the 

 large anterior and posterior muscles of the second valvifers (oblong 

 plates) that have their origins on the quadrate plates of the ninth 

 tergum (fig. 47 A, i/, 18). The homologues of these muscles are 

 readily identified in all pterygote insects ; in the Hymenoptera the 

 fibers of the first muscle are separated into two distinct groups {lya, 

 i/b), but they are all inserted on the anterior arm of the second valvi- 

 fer or on the upper extremity of the ramus of the second valvula. The 

 posterior muscle (18) arises anteriorly and dorsally on the inner face 

 of the quadrate plate, and its fibers converge posteriorly and ventrally 

 to their insertion on the posterior end of the elongate second valvifer. 

 These two sets of muscles are antagonistic to each other because the 

 fulcrum of the second valvifer on the first valvifer (&) lies between 

 their attachments on the former plate. 



