vin] SOME STRUCTURAL FEATURES 109 



irritant poison is injected into the enemy, but merely 

 the protecting sheath, known as the "director," which 



N.P 



Fig. 18. Ventro-lateral view of sting of Vespa germanica ? : the 

 needle (N.) of the far (right) side has been withdrawn and is 

 shown below the other structures 



D., director. E., ventral inturned edges of director. G.H., G.H'., 

 guiding hairs of left and right sides. G.S., guiding studs on 

 inner face of D. L.D., L.D'., levers of left and right sides for 

 extrusion of D. L.N'., L.N., levers for extrusion of left and 

 right needles, N'., N., beyond tip of D. N., right needle with- 

 drawn from D but lying parallel to its original position. N'., 

 anterior part of left needle ; the remainder lies concealed within 

 D. N.P., N.P'., piston (?) enlargements on right and left needles. 

 S., stout chitinous piece on dorsal surface of D. The arrows 

 show the direction in which the muscles pull the levers when the 

 sting is employed. The poison sac and duct are not shown. 



prepares the way by penetrating the tougher epider- 

 mis, and guides the really effective weapons into the 



