134 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 89 



posteriorly and ventrally to ventral wall of proctiger, where one {21) 

 is inserted laterally, the other {22) medially. 



The mechanism of the sting. — When a worker bee is held securely 

 by the thorax, preferably in a pair of forceps, her ineffectual attempts 

 to use the sting are accompanied by a strong deflection of the end of 

 the abdomen. The shaft of the sting is thrust out from the cleft 

 between the tergal and sternal plates of the seventh segment, and 

 slides back and forth in the terminal notch of the sternum. The ex- 

 posure of the shaft is usually greatest as the direction of the thrust 

 approaches a perpendicular to the axis of the body ; the seventh 

 sternum is depressed and the bulb of the sting appears in the opening 

 above it. The third valvulae, or so-called " palpi " of the sting, are not 

 in evidence while the shaft is probing for an object to strike, and the 

 writer has never observed any use made of these organs by the bee 

 to suggest that they have a tactile function, or that by means of them 

 the bee determines where a vulnerable spot is presented for her at- 

 tack, as she has been supposed and even said to do. The third valvulae 

 do not issue from the sting chamber. The highly mobile abdomen 

 swings around in all directions on the petiole, and the decurved tip 

 strikes at random until an object is encountered, which, if nothing 

 else presents, may be the body, head, or mouth of the bee herself. 



The deflection of the terminal part of the abdomen is brought about 

 by the contraction of the oblique lateral intertergal dorsal muscles 

 (fig. 39, dil) and the median intersternal ventral muscles (vim) of 

 the segments concerned. The accompanying movements of the ab- 

 domen as a whole depend upon the mechanism of the petiole and are 

 produced by the muscles of the propodeum inserted upon the second 

 segment. 



The entire act of stinging involves three separate movements, or 

 sets of movements, in the sting apparatus. The first accomplishes the 

 outward thrust of the shaft, the second the depression of the shaft, 

 and the third the movements of the lancets on the stylet. The first 

 two movements are simultaneous, but each has its own mechanism, 

 while the movement of the lancets depends on a third mechanism quite 

 distinct from the other two. 



When the bee persists in her attempts to sting an inaccessible or 

 nonexistent object, the shaft, as we have seen, glides rapidly back 

 and forth in the notch of the seventh sternum, and with each outward 

 thrust is exposed for nearly its entire length. If now, while the bee 

 is held under the microscope, the plates of the apical segment are 

 separated with a needle or a pair of slender forceps, it is to be seen 

 that the movements of the shaft are produced by corresponding move- 



