CLASS-BOOK OF ZOOLOGY. 149 



SECTION XXXIX. 



7lh Order — Wingless Insects : (Aptera.) 



§ 639. Insects without wings differ very much in re- 

 gard to their size, form, and the number of their feet ; 

 and do not undergo a metamorphosis, like the preceding 

 orders, the Flea excepted. 



§ 640. To this Order belong the Louse, Flea, Tick, 

 Spider, Scorpion, Crab, Lobster, Centipede, etc. 



§ 641. The Louse (Pediculus) is probably one of the 

 most extensively diffused genus of Insects. Most Mam- 

 malia and birds have Lice of peculiar kinds ; and fishes, 

 and even some insects, are also plagued in the same way. 



5 642. The Flea (Pulex) lays about twenty eggs, from 

 which, after six days, proceed very small white maggots, 

 of a serpentine form. These, after fourteen days, are 

 metamorphosed into a puppa ; from which, after fourteen 

 days more, proceeds the perfect Flea. It is found on man, 

 the dog, fox, squirrel, hare, and hog. 



$ 643. The Tick (Acarus) lives in forests upon plants, 

 and fastens itself on passing Mammalia, principally, dogs, 

 horses, sheep, and even on man. It thrusts its fore-feet 

 and proboscis into the skin of the animal to which it 

 attaches itself, in order to suck its blood ; but by besmear- 

 ing them with olive-oil, they quickly fall off. 



§ 644. The Spider (Aranea) has eight feet, and is 

 armed, like a venomous snake, with two moveable fangs ; 

 and through these, which are horny, hollow, and crooked, 

 the venom is injected into the wound it inflicts. 



§ 645. The bite of small Spiders produces only an itch- 

 ing, that of the large ones an unpleasant inflammation ; 

 but in spite of all this, people have been known to eat 

 them, with bread, as a delicacy. 



§ 646. Spiders are found throughout the world. The 

 greater part of them weave webs which are deserving of 

 special notice for the regularity of their structure, and 

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