78 
STING STRUCTURE. 
which is a transverse section through the point at which 
the two pieces forming this valve are attached, and shows 
the opening between them to the interior cavity of the 
lancets, through which the poison enters the moment 
this valve closes the channel between the lancets by 
striking into the angles of the sheath at c (Pdg. 35, b). 
The valves consist of two semicircular pieces (f, e), 
fixed by their loose edges to the lancets (c d)^ the 
straight sides being uppermost, thick and chitinous. 
These pieces are braced together by a heavy curved 
plate (<^), extending from them to its attachment with 
the lancet. 
The poison, which is contained in the sac (Fig. 34, 
/), and is in the worker a clear liquid, pours its con- 
tents into the large chamber of the sheath, and by the 
action of the valves is forced into the wound through 
the canals in the lancets, and out at the openings be- * 
tween the barbs, with considerable force. 
Carlet ( 20 ) found that the two lancets of the 
sting may move simultaneously or alternately ; but in 
either case the valves, which act as a piston, can at 
each stroke force out a drop of poison, and at the 
same time a fresh afflux of liquid is produced at the 
base. The apparatus acts like a syringe, and by its 
two pistons, d parachute^ it drives out by the canula 
the liquid which it draws in at its base. 
The lever mechanism which enables the bee to 
drive its sting right up to the bulbous enlargement 
with such force will be understood by reference to 
Fig. 34. The darts are attached at c to the levers b. 
The levers, c and d, are furnished with broad muscles. 
