538 The Animal Kingdom 



Order 2. Diplura (Campodeids and Japygids). Wingless blind, slender, 

 small forms. Long antennae, pair of conspicuous cerci at posterior 

 end which are either segmented or forcepslike. Metamorphosis in- 

 conspicuous. Occur under leaves, etc., in moist areas. Of no eco- 

 nomic importance; about 100 species. 

 Group Pterygota. Winged forms. Varied forms in this group. 

 Series Hemimetabola. Metamorphosis gradual or incomplete. 

 Order 1. Ephemeroptera (Mayflies). Aquatic nymphs which when ma- 

 ture rise to the surface, and emerge as winged forms. Adults short- 

 lived, eat no solid foods, emerge in tremendous swarms during which 

 mating occurs. Of great economic importance as a food for fish in 

 fresh waters; about 1,300 species. 

 Order 2. Odonafa (Dragonflies and Damsel Flies). Nymphs aquatic, 

 but do not swim; instead walk on bottom. Nymphal development 

 takes from one to four years. When mature, crawl to a stick or 

 other object for last molt. Both adults and nymphs are predaceous. 

 Important as fish food and for destruction of various insects ; about 

 4,500 species. 

 Order 3. Orthoptcra (Cockroaches, Grasshoppers, Mantids, Walking 

 Sticks, Crickets, Grouse Locusts, Mole Crickets). Winged forms 

 with two pairs of net -veined wings; others lacking wings. Chewing 

 mouth parts, many forms omniverous. Many of great economic im- 

 portance, including cockroaches as pests in dwellings, grasshoppers for 

 their destruction of crops, mantids for their destruction of harmful 

 insects ; about 23,000 species. 

 Order 4. Dennaptera (Earwigs). Medium-sized insects with a pair of 

 heavy forceps at the posterior portion of the abdomen. Mouth parts 

 chewing, wings at times lacking ; if present, fir,st pair heavy, veinless ; 

 second pair fan-shaped. Chiefly tropical forms with a few northern 

 species. One species, the European earwig (Forficida auricularia) 

 is destructive to many flowers. About 1,100 species. 

 Order 5. PIccopfera (Stone Flies). Medium-sized insects with aquatic 

 nymphs. With chewing mouth parts, long antennae, both pairs of 

 wings well developed, nearly always present. 1,500 species. 

 Order 6. I so pt era (Termites, White Ants). Social insects, with several 

 castes, feed on cellulose. Of great economic importance due to 

 their destruction of wood in buildings. 1,600 species. 

 Order 7. Corrodentla (Psocids). Very small terrestrial forms with 

 chewing mouth parts. Some with well-developed wings ; in others they 

 are much reduced or absent. Many of economic importance due 

 to waste of food and damage to libraries. Mainly they feed on 

 molds, lichens, etc. 1,100 species. 

 Order 8. Mallophaga (Bird Lice, Chewing Lice). Small to medium, 

 wingless, flattened insects; ectoparasites of birds and mammals, with 

 chewing mouth parts, short antennae. A single species usually oc- 

 curs only on one species of host. Feed on scaly skin, bits of hairs 

 and feathers, blood, etc. Eggs glued to hair or feathers. Of great 

 economic importance as ectoparasites. About 2,500 known species. 



