It is moreover remarkable, that their mandibles are perforated and pour a poisonous juice into the wounds they inflict. They must be therefore regarded, like the venom-teeth of Serpents, as elongated salivary ducts.
The Crustacean families can also be named according to the orders of their circle, namely, the Worms and Crustacea, e. g. thus:
Order I. Worm-Crabs—Pfriemenkrebse.
Fam. 1. Entozooid—Mussel-Insects.
2. Hirudinous—Branchiopoda.
3. Holothurioid—Shield-Crabs.
Order II. Crustacean Crabs—Scheerenkrebse.
Fam. 4. Typical Crustacea—Sea-Mantes.
5. Asselkrebse " —Macrura.
6. Arachnoid " —Brachyura.
Ninth Class.
Tracheal, Alary Animals—Flies.
Typical Ancyliozoa.
3517. Body tripartite, only three pairs of thoracic legs, spiracula and wings. They divide, according to the classes of their circle, into three cohorts, of Worm-, Crab-like, and perfect Flies.
As the wings are their characteristic organ, so also must they be divided according to them, and not after the cibarial instruments. Those wings which are developed to the least degree are the homogeneous, transparent wings traversed by few tracheæ or ducts—Tracheoptera, as Flies, Bees, and Butterflies.
Their chrysalis or pupa condition is perfect.
Then follow wings having very numerous veins united by transverse veins so as to form a network—Dictyoptera, as Neuropterous, Orthopterous, and Hemipterous Insects.