SYSTEM OF INSECTS. 393 



insect tribes* : but our business now is with those Aptera 

 whose body consists of 'three greater segments, and which 

 in none of their states have ever more or less than six 

 legs, and consist of the three Linnean genera Pediculus, 

 Lepisma, and Podura ( TTiysanura and Anoplura). Some 

 of the mites (Acarus L.) are hexapods, but their body 

 has no distinction of head, trunk, and abdomen. The 

 metamorphosis of most female Blatttf, and of some other 

 Orthoptera that are apterous, cannot be regarded as 

 materially different from that of the Hexapods. Amongst 

 the Anoplura^ the Pediculi^ or lice, are suctorious, and 

 the Nirmi, or bird-lice, masticators, a circumstance 

 which in them does not appear to indicate even a diffe- 

 rent Order, and proves that undue stress ought not to 

 be laid, independently of general characters, on the mode 

 in which insects take their food. 



DEF. Metamorphosis complete. 



Body consisting of three principal segments. 

 Mouth perfect, or rostellate b . 

 Antenna distinct. 

 Legs six, in every state. 



Octopods. This suborder consists of the Trachean 

 Arachnida of Latreille, excluding the Pycnogonida.; of 

 the Acaridea, Sironidea, Phalangidea, and part of the 

 Scorpionidea of Mr. MacLeay, and, with some excep- 

 '4ms, of the Linnean genera Acarus and Phalangium. 

 This last tribe (for with Linne, I include Chelifer and 

 Obsidium in the Phalangidea^) on one side approaches 

 Scorpio by Thelyphonus, and on the other the Aranidea 



8 VOL, III. p. 22, h Ibid. p. 471. 



