184- INTERNAL ANATOMY OF INSECTS. 



cartilage. In the grub of Dytiscus the power and mag- 

 nitude of the adductor muscle is wonderful a . In the 

 Orthoptera this structure of the mandibular muscles takes 

 place also in the imago b ; but in the Coleoptera, at least 

 in the stag-beetle and some others that I have examined, 

 these muscles in this state have no cartilage or tendon. 

 Their attachment is alwtiys to the parietes of the head, 

 of the cavity of which the adductors^ in some cases, oc- 

 cupy a considerable portion c . As to their insertion 

 these last, in some Orthoptera^ enter more or less the in- 

 terior of the mandible d ; but commonly they are inserted 

 at or near the interior angle of the mandibular basal ca- 

 vity, and the abductors at the exterior. 



ii. The Trunk. We have little information with re- 

 gard to the muscles of the parts of the trunk itself, by 

 which, in some insects, the manitrunk is enabled to 

 move independently of the alitrunk : it is more probable 

 that the levators have in part at least their attachment 

 to the anterior surface of the prophragm % than that the 

 levators of the head should be there fixed, as Cuvier 

 seems to think ; since both the phragma and the ligament 

 that appears in many cases to close the cavity of the 

 manitrunk round the viscera f , would prevent all com- 

 munication between those muscles and any part con- 

 nected with the scutellum : probably the depressors have 

 their attachment partly on the anterior face of the medi- 

 furca $. These points, however, must be left to future 

 investigators. 



3 De Geer iv. t. xv./. \\.o t p. 



b Marcel cle Serres Comparaison, fyc. 3 . c Ibid. 4. 



o Ibid. 5. c PLATE XXII. FIG. 11. h' . { VOL. III. p. 579. 



s PLATE XXII, FIG. 6. VOL, III. p. 585. 



