The Life Processes of the IndividvM 



159 



bulb {ShB) and is further continued in two arms {ShA) 

 which curve outward. The lancets slide on a grooved 

 track the full length of the sheath, past the bulb and diverge 

 along the two basal arms. The sheath and lancets combine 

 to form a hollow tube (PsnC) through which the poison 

 flows. 



The arms of the sheath are attached at their anterior 

 ends to oblong plates (Ob) which overlap the sides of the 

 sting. To these plates 

 are attached palpi 

 (StnPlp), soft white pro- 

 jections provided with 

 sense organs, by means 

 of which the bee can 

 tell when she is in con- 

 tact with the object 

 which is to be stung. 

 The lancets are attached 

 to triangular plates (Tri) 

 which in timi articulate 

 with the quadrate plates 

 (Qd). By the move- 

 ments of these plates on 

 each other the lancets 

 are slid along the sheath 

 when the sting is used. 

 It has been shown by 



Zander * that the triangular plate {Tri) is part of the 

 eighth sternum, the quadrate plate (Qd) is part of the 

 ninth tergum and the oblong plate (Qb) is the ninth 

 sternum. 



"In the accessory plates of the bee's sting we have a 

 most excellent illustration of how parts of a segment may 

 become modified to meet the requirements of a special 

 function, and also an example of how nature is ever reluctant 



• Zander, Enoch, 1899. Beitrage zur Morphologic des Stachelapparates 

 der Hymenopteren. Zeit. f. wiss. Zool., LXVI, pp. 288-333. 



Fig. 83. — Ventral view of sting of worker 

 and accessory parts, flattened out. 



