136 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 89 



rounding parts, and particularly by the ample length of the membran- 

 ous floor of the sting chamber reflected from the seventh sternum. 



The relative changes in position of the various parts of the sting 

 apparatus before and after the protrusion of the shaft are shown at 

 D and E of figure 46. The axis of revolution in the basal parts passes 

 through the upper ends (/) of the quadrate plates (IXT), which are 

 overlapped by the spiracular plates (Lsp) of the eighth segment. The 

 spiracular plates themselves are but little affected by the movements 

 of the sting, since they are held in place by their dorsal and ventral 

 muscles (i, 8). In the position of protraction (E) the sting base is 

 almost at right angles to the lower margins of the spiracular plates, and 

 the sheath lobes, or third valvulae (3VI), are pointed upward. The 

 shaft of the sting, on the other hand, has retained its position in the 

 direction of the thrust by a movement of depression. The depression 

 of the shaft somewhat flattens the curve of the rami (ra), and is 

 accompanied by an eversion of the membranous ninth venter, which 

 now appears as a large hairy lobe (I XV) over the bulb of the sting. 



The mechanism of the stinging apparatus of the bee was first studied 

 by Sollmann (1863), who observed that the outward thrust of the 

 shaft is produced by a backward swing of the supporting basal parts. 

 His explanation of the movements of the latter, however, is mostly 

 fanciful, since he attributes them to muscles that either do not exist 

 or do not have the attachments he ascribed to them. It was later shown 

 by Kraepelin (1873) that there are no muscles immediately connected 

 with the sting or its basal support that can give the movements of 

 protraction and retraction to the shaft. Accepting this fact, Kraepelin 

 says : " Ich nehme daher keinen Anstand. als treibendes Princip f iir 

 die Bewegung des Stachels im engeren Sinne die Blutfliissigkeit zu 

 bezeichnen, welche ja auch bekanntermassen bei den Hervorstulpen 

 des Penis und ahnlicher Korperanahange eine so wichtige Rolle spielt. 

 Bei jeder stechenden Biene kann man eine seitliche Annaherung der 

 Abdominalwandungen mit Lichtigkeit beobachten, bei frisch getodeten 

 aber geniigt ein geringer Druck auf die vordern Hinterleibssegmente, 

 um den Stachel in normaler Weise hervortreten zu lassen." 



A careful examination of the bee confirms the truth of Kraepelin's 

 statement concerning the lack of any special muscles for the protrusion 

 and retraction of the sting, and makes it clear that the shaft is driven 

 out of the sting chamber by pressure exerted against the membranous 

 walls of the latter from within the body cavity of the abdomen. The 

 rotund anterior part of the postabdomen, by a bulblike action of com- 

 pression and expansion, thus swings the basal support of the sting back 

 and forth on its points of suspension at the dorsal angles of the quad- 



