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 Jarve there is a pair in the first 
segment of the trunk. This is also to be found in the other 
states, but is not easily detected in the pupe of Lepidop- 
tera: in the Coleoptera order, in the grub of the Lamel- 
licorn beetles, it is extremely conspicuous, and planted in 
the side of the first segment*; in other Coleopterous grubs 
it is not so readily found, but probably its station is some- 
where behind the base of the arms, where it is very visi- 
ble in that of Staphylinus. In the zmago of insects o. 
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 ower 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 common rove-beetle, however, 
(Staphylinus olens) you may easily see it without dissec- 
tion’. In the Orthoptera it is situated behind the arms, 
® Swammerd. Bidl. Nat. t. xxvii. f.5. Compare Sturm Deutsch. 
Peer tavene 3. 
> Prats XXIX. Fic. 12. c’. 
