114 The Piercing Apparatus. 



of this muscle, the posterior plate is drawn towards the 

 anterior one, and thus the protruded spiculae are again 

 withdrawn. In this way this muscle is the antagonist 

 of the last one. 



Ps. fifth muscle springs from the margin of the notch in 

 the anterior plate, near the third muscle, the action 

 of which it supplements. 



Owing to their concealed position, it is not possible 

 to observe how these muscles act in the living fly, but 

 the movements of the insect as they occur in egg-laying 

 can nevertheless be seen. They may be watched very 

 plainly in Neuroterus laeviusailus. The long ovipositor 

 of this fly (PI. Ill, Fig. 2) hidden in the abdomen during 

 repose, comes perfectly into view while ovipositing, and 

 the two pairs of plates are seen at the same time. 

 But as the exact movements of the spiculae are only 

 observable during the slight protrusion of the plates, it 

 is necessary that we should have the plates exposed in 

 order to observe the character of these movements 

 properly. This may be demonstrated in the following 

 way. Wait until the Neuroterus laeviusculus pricks the 

 bud, and when the ovipositor has penetrated into the 

 bud, try by a quick movement to pull the fly off; the 

 ovipositor is too firmly fixed, resists, and breaks off \ 

 There remains connected with it the whole motor 

 apparatus, and also the large ganglion which innervates 

 the muscles ; consequently the pricking movements 

 proceed regularly until the muscles die. It is then 



[^ Lichtenstein states that this often takes place when the flies are 

 at liberty, and in spring he had frequently found the ovipositor and 

 part of the abdomen of a cynips fixed in a bud.] 



