NO. 8 INSECT ABDOMEN SNODGRASS IO3 



J. Second levator of the first valvifer (fig. 33 C). — A tergo- 

 pleural muscle of the eighth segment, arising on lower part of an- 

 terior margin of eighth tergum ; inserted anteriorly on dorsal apo- 

 deme of first valvifer. This muscle is accessory to the last, and both 

 2 and J are clearly antagonistic to i. 



.4. Muscle of the first valvula (fig. 33 B). — A thick bundle of 

 short fibers arising on inner face of first valvifer (iVlf) ; inserted 

 posteriorly and mesally on inner plate (w) of base of first valvula. 

 This muscle appears to be antagonistic to 2 and 5, and accessory to i. 



5. Conjunctival muscle (not shown in the figures). — A short thick 

 muscle arising dorsally on lateral part of eighth tergum; fibers con- 

 verging downward to insertion on intersegmental membrane between 

 eighth and ninth segments above and posterior to eighth spiracle 

 (fig. 31 A, VI lisp). This muscle apparently serves to inflect the 

 wide membrane between the segments. 



6. Anterior muscle of the second valvifer (fig. 34). — A flat tri- 

 angular sheet of strong fibers arising mediodorsally in longitudinal 

 series on ninth tergum ; insertion ventrally on anterior apodeme 

 (g) of second valvifer and on extreme anterior end of the valvifer. 

 The contraction of this muscle rotates the second valvifer upward 

 anteriorly on the tergal fulcrum (p) and retracts the second valvula. 

 It is the homologue of muscle 6 of Gryllus (fig. 17E, G) and of 

 Amblydisca (fig. 28 D). 



7. Posterior muscle of the second valvifer (fig. 34). — A huge fan 

 of several thick bundles of fibers arising dorsally on ninth tergum, 

 laterad of 6; inserted ventrally on dorsal part of second valvifer 

 posterior to the tergal fulcrum (p). This muscle is antagonistic 

 to the anterior muscle (6), and protracts the second valvula by de- 

 pressing the anterior end of the valvifer. It is the homologue of 

 muscle 7 of Gryllus (fig. 17E, G) and Amblydisca (fig. 28 D). 



The first valvifers can respond freely to the contraction of the 

 muscles inserted upon them because of the flexible nature of their 

 posterior connections with the ninth tergum. The effect of the mus- 

 cles inserted on the dorsal apodemes of the valvifers (fig. 33 C, t, 

 2, s) is only to elevate and depress the anterior ends of the plates. 

 In a dissected specimen these movements of the first valvifer cor- 

 respondingly depress and elevate the entire ovipositor, and there can 

 scarcely be any question that they serve to unsheath and resheath 

 the ovipositor preceding and following its use in oviposition. The 

 short muscle from each first valvifer to the inner plate of the first 

 valvula (B, 4) is apparently accessory to the depressor of the val- 

 vifer (C, i), since, when the ovipositor is depressed, the valvifer 



