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 larvae there is a pair in the Jirst 

 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 Coleoptera 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, where 

 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 lower 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, ( Goerius olens] you may easily 

 see it without dissection 13 . In the Orthoptera it is situated 

 behind the arms, as in Gryllotalpa : or between them 



a Swammerd. Bibl. Nat. t. xxvii./. 5. Compare Sturm Deutsch. 

 Fn. \. t. v./. r. " PLATE XXIX. FIG. 12. c'. 



