SYSTEM OF INSECTS. 393 
insect tribes 3 : but our business now is with those Aptcra 
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 ( Tfiysanura 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 Blattce, 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- 
<fons, of the Linnean genera Acarns and Phalangium. 
This last tribe (for with Linne, I include Chelifer and 
Obsidium in the Phalangidca,) on one side approaches 
Scorpio by Thclyphonus, and on the other the Aranidea 
' Vol. III. P . 21 h Ibid. p. 471. 
