The Piercing Apparatus. T13 



of the seta (called by Kraepelin the horn). By its con- 

 traction this muscle draws upon the horn, and thus 

 raises the seta from the position it occupies in repose, 

 and directs it downwards : this is the first introductory 

 movement in ovipositing. 



The second, a smaller muscle, also takes its origin 

 from the anterior plate, chiefly from the arch, and is 

 inserted by a long chitinous tendon into the base of the 

 horn near the last muscle. The contraction of this 

 muscle draws the seta towards the anterior plate, and 

 it is thus the antagonist of the former one. This 

 muscle also varies greatly in strength, being sometimes 

 reduced to a few fibrillae ; in Neuroterus laeviusciihis it 

 is entirely wanting, and the first muscle is also very 

 feebly developed in this fly. 



The third, a powerful muscle, arises from the hamu- 

 lar process of the anterior plate and from the margin 

 of the notch in which the angular plate lies ; it is 

 inserted, by a long line of attachment, into a strong 

 chitinous ridge on the posterior plate. The contraction 

 of this muscle draws the posterior plate upwards. This 

 movement is communicated to the angular plate, and to 

 the spiculae connected with it, and the result is that 

 these latter are thrust forward. This movement is of 

 the greatest importance, for it is by the spiculae, when 

 thus thrust forward, that the first opening is made, 

 through which the whole ovipositor is pushed into the 

 tissues of the plant. 



P^ fourth very powerful muscle springs from the pro- 

 jecting rim of the anterior plate and is inserted into the 

 upper half of the posterior plate. By the contraction 



I 



