NO. 8 



INSECT ABDOMEN SNODGRASS 



141 



Because of the double articulation of the first valvifer on the 

 quadrate plate and the oblong plate (fig. 48 A), and of the difference 

 in length between the two axes (ab and ac) of the valvifer, a very 

 small movement of the quadrate plate (B, d) produces a relatively 



Fig. 48.— Diagrams of a model of the sting of the honey bee to show the 

 mechanism of retraction and protraction of the lancets. 



A, the lancet retracted by contraction of ventral muscle (18) of quadrate 

 plate (IXT) attached posteriorly on oblong plate {sVlf). 



B, the lancet protracted by contraction of dorsal muscle (//) of quadrate 

 plate attached anteriorly on oblong plate. 



large movement of the lancet. In the living bee the motion of the 

 quadrate plate appears as a quivering or rapid back-and- forth vibra- 

 tion, its actual displacement being scarcely perceptible. When the 

 sting is extracted, however, with the shaft in the wound, the motion 

 of the quadrate plates is greatly increased. 



