The Piercing Apparatus. iii 



abdomen. These plates may be distinguished as the 

 anterior (outer) and posterior (inner) plate, a description 

 which is perfectly clear when the ovipositor is placed as 

 it lies in the abdomen of the fly. The accompanying 

 illustrations (Plate III) exhibit the ovipositor always in 

 this position. An examination of the drawings will 

 show that these chitinous plates are found in a great 

 variety of forms, and this variation gives to each 

 species its characteristic formation of ovipositor ; but 

 the connexion between them and the terebra is always 

 the same, and the groups of muscles are alike in every 

 ovipositor. 



Their connexion with the terebra is as follows — at 

 the origin of each spicula is a broad and almost 

 triangular plate, the angular plate ^ of Kraepelin, which 

 is articulated with the anterior and posterior plates by 

 hinge-joints, but the articulation with the posterior 

 plate is freer and more moveable than with the 

 anterior. This double articulation of the two spiculae 

 has the obvious advantage of enabling them to be 

 thrust to and fro, while they are at the same time 

 securely maintained in position. 



There are certain groups of muscles which set the 

 spiculae in motion, but these act primarily through the 

 two plates to which they are articulated. Each muscular 

 contraction causes a movement of the plates which is 

 transmitted to the triangular plate, and thence the motion 

 is communicated to the spiculae by their connexion with 

 the triangular plate. A to and fro movement of the 

 spiculae is thus the only possible one, and at the same 



1 Winkel. 



