INTERNAL ANATOMY OF INSECTS. 43 
caterpillars these organs are generally planted between 
two spines, one being above and the other below. The 
lateral line of the body most commonly marks their si- 
tuation ; but in many cases they become ventral, and in 
others dorsal. The most important circumstance, how- 
ever, connected with the present head is their appropria- 
tion to particular segments or parts of the body, for, like 
the ganglions of the spinal marrow, they are distributed 
to almost every segment. Let us take a summary view 
of their arrangement in this respect. 
No insect has any spiracle in the head ; but in cater- 
pillars and many other larva there is a pair in thejirst 
segment of the trunk. This is also to be found in the 
other states, but is not easily detected in the pupce of 
Lepidoptera : in the Coleoptcra order, in the grub of the 
Lamellicorn beetles, it is extremely conspicuous, and 
planted in the side of the first segment a ; in other Coleo- 
pterous grubs it is not so readily found, but probably its 
station is somewhere behind the base of the arms, whei'e 
it is very visible in that of the Staphylinidce. In the 
imago of insects of this order, this antepectoral spiracle 
has been overlooked, and indeed is not soon discovered : 
to see it clearly, the manitrunk should be separated from 
the alitrunk ; and then if you examine the lovoer side of 
the cavity, you will see a pair of, usually, large spiracles 
planted just above the arms, in the ligament that unites 
these two parts of the trunk to each other : in the com- 
mon rove-beetle, however, (Gocrius olens) you may easily 
see it without dissection 15 . In the Orthoptera it is situated 
behind the arms, as in Gryllotalpa : or between them 
» Swammerd. Bibl. Nat. 1. xxvii./. 5. Compare Sturm Deutsch. 
Fh. i. /. v./. r. b Plate XXIX. Fig. 12. c'. 
