184- INTERNAL ANATOMY OF INSECTS. 
cartilage. In the grub of Dytiscus the power and mag- 
nitude of the adductor muscle is wonderful". In the 
Orthoptera this structure of the mandibular muscles takes 
place also in the imago b ; but in the Colcoptera, 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 always to the parietcs 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 thescutellum : probably the depressors have 
their attachment partly on the anterior face of the medi- 
furca s. These points, however, must be left to future 
investigators. 
a De Gcer iv. t. xv./. 11. o, p. 
h Marcel de Serres Comparaison, <Src. 3 — . c Ibid. 4. 
" Ibid. 5. c Plate XXII. Fig. 11. A'. f Vol. III. p. 5/9. 
b Plate XXII. Fig. 6. Vol. III. p. 585-. 
