The Life Processes of the Individual 
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 turn 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 tcrgum and the oblong plate (Ob) 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 
1 Zander, Enoch, 1899. Beitr&ge znr Morphologic des Stachelapparates 
der Hymenopteren. Zeit. f. wiss. Zool., LXVI, pp. 2S8-333. 
Fig. 83. — Ventral view of sting of worker 
and accessory parts, flattened out. 
