242 CLASSIFICATION OF PLANTS AND ANIMALS 



Class I. Crusta'cea. They live mostly in the water and breathe by means of gills. The head 

 and thorax are fused into a hard covering. They have a "crusty" exoskeleton, strength- 

 ened with lime. Examples : crabs and lobsters. 

 Cl.\ss II. Myriap'oda (thousand legs). They have long bodies with many segments and 



many paired jointed appendages. Centipedes and millepedes are examples. 

 Class III. Insec'ta. The largest of all classes of animals (over 450,000 species). Body seg- 

 mented ; three regions : head, thorax, and abdomen. Three pairs of jointed legs. Usually 

 compound eyes. Breathe through tracheae or air tubes. There are 20 orders, but usually 

 examples of only the following eleven orders are found. 

 Order 1. Ap'tera (without wings). Very simple insects without wings; with biting mouth 

 parts. Examples, springtails and "silver fish" or fish moths, which are found frequently 

 in houses. 

 Order 2. Ephemer'ida. Insects having complete metamorphosis and biting mouth parts. 

 They have long setae which project from the end of the abdomen. The adult lives only 

 a day or two, lays eggs, and dies. The mayflies. 

 Order 3. Odon'ata. Complete metamorphosis. Biting mouth parts. Adults are expert 



flyers, have large eyes, live mostly in water. Dragon flies and damsel flies. 

 Order 4. Or</iop'iera (straight wings). Four wings, front pair straight and leathery. Biting 



mouth parts. Grasshoppers, crickets, cockroaches, walking sticks, etc. (Page 27.) 

 Order 5. Coleop'tera (sheath wings). Hard outer wings, forming cover for under wings. 

 Biting mouth parts. Complete metamorphosis. All beetles, "June bug," firefly, etc. 

 Order 6. H emip'ter a (hali wings). Sucking mouth parts. Complete metamorphosis. Two 



pairs of wings or none. True "bugs, "squash bug, plant lice, scales, cicada. 

 Order 7. Neurop'tera (veined wings). Four membranous wings with many veins. Biting 



mouth parts. Complete metamorphosis. Ant lions, dobson fly, etc. 

 Order 8. Dip'tera (two wings). Insects with two wings, a few with none. Mouth parts 

 fitted for sucking or piercing. Complete metamorphosis. All flies, mosquitoes, gnats, etc. 

 There are 40,000 described species and it is estimated that there are more than 300,000 

 as yet undescribed. 

 Order 9. Siphonap'tera (tube; wingless). Largely parasitic. Sucking mouth. Wings if 



present much reduced in size. Complete metamorphosis. Fleas. 

 Order 10. Hymenop'tera (membrane wings). Four membranous wings. Mouth parts 

 fitted for biting and sucking. Often long ovipositor modified into sting. Complete 

 metamorphosis. Bees, ants, and wasps, gall and ichneumon flies. (Page 26.) 

 Order 11. Lepidop'tera (scale wings). Four wings, covered with scales. Mouth parts 

 long sucking tube. Complete metamorphosis. Moths and butterflies. 

 Class IV. Arachnida (a-rak'ni-da) . This group has no antennse, four pairs of legs, and a 

 pair of claw-like appendages on each side of the mouth. Head and thorax combined as in 

 Crustacea. The spiders, "daddy-long-legs," scorpions, mites, and ticks are in this class. 



IX. MoUus'ca (Lat. mollis, soft). — These are soft-bodied animals, often 

 provided with a shell, which is secreted by a part of the body called the mantle. 

 They usually have a single muscular foot on the ventral side. Over 60,000 

 species are known. There are three classes. 



Snail 



Oyster 

 Mollusca. 



Squid 



