266 . TEXTBOOK OF ZOOLOGY 



Order Corrodentia, book lice. 



Order Mallophaga, bird lice. 



Order Anoplura, body lice ("cooties"), crab louse. 



Order Hemiptera, true bugs, as squash bug. 



Order Romoptera, plant lice, scale insects, cicadas. 



Order Neuroptcra, aphis lions, ant lions. 



Order Trichoptera, caddis flies. 



Order Lepidopiera, butterflies and moths. 



Order Mecoptera, scorpion flies. 



Order Dipt era, true flies, mosquitoes. 



Order Siphonaptera, fleas. 



Order Hymenoptera, wasps, ants, bees. 



Division C. Arachnoidea (ar ak noi'de a, spiderlike). A group 

 without antennae but Avith tracheae, book lungs or book gills, and 

 four pairs of thoracic appendages. 



Class V. Arachnida, spider, mite, scorpion, king crab, etc. 



Order Scorpionida, scorpions. 



Order Pedipalpi, vinegarroon and tarantula. 



Order Pseudoscorpionida, book scorpion. 



Order Phalangida, daddy longlegs or harvestmen. 



Order Palpigradi, one Texas species. 



Order Araneida, spiders. 



Order Acarina, ticks and mites. 



Order Xiphosura, king crab or horseshoe crab. 



This summary of the classification of the phylum has been placed 

 early in the chapter in order that the student may realize the mag- 

 nitude of its size and the great variety of animals included. The 

 number of species described under the phylum is approximately 

 one-half million, and there are large numbers still undescribed and 

 unnamed. 



CRAYFISH OF CLASS CRUSTACEA 



Since this animal represents a relatively simple type of arthropod 

 and is so generally well known, it serves ideally as a representative 

 species for a more detailed study. The genera Canibarus and 

 Potamdhius or Astacus are commonly found in the streams of North 

 America. The former is distributed east of the Rocky Mountains and 

 the latter on the Pacific slope. 



