i6a ECONOMIC ZOOLOGY AND ENTOMOLOGY 



eyes, and in this and their winglessness show the degeneration 

 which a parasitic life almost always produces. The eggs are 

 fastened to the hairs or feathers, and the young undergo little 

 change during their development except an increase in size to 

 become like the parents. 



Almost every species of bird or mammal is infested by one 

 or more kinds of Mallophaga, and some- 

 times the host must suffer much annoy- 

 ance and even injury from the irritation 

 produced by its many small parasites. 

 All of the common barnyard birds are 

 troubled more or less by these biting lice, 

 and their presence may become a serious 

 matter in hen-houses. An account of cer- 

 tain special Mallophagan pests and of 

 remedies for them is given in Chapter 

 XXXVII. 



Order Orthoptera. The order Ortho- 

 ptera is much larger than any of the other 

 orders so far considered, and includes 

 many familiar insects, such as the grass- 

 hoppers, katydids, crickets, cockroaches 

 and praying mantises. The order is di- 

 vided into six families, of which three in- 

 clude all the well-known singing insects, 

 except the cicada or harvest flies. The 

 insects in these three singing families are 

 also the best known leaping insects, the 

 hind legs being especially long and strong, 

 so that when the insect is at rest the 

 "knee joints" of these legs stand up conspicuously above the 

 body. 



All the Orthoptera have strong biting mouth-parts and nip 

 off and chew their food, which is usually green leaves and stems. 

 The mantises (family Mantidce) are, however, predaceous, 

 preying on other insects, and the cockroaches (family Blattidia) 

 prefer dried vegetable or animal matter. The metamorphosis 

 is incomplete, and the young, which resemble the parents 



FIG. 75. A biting 

 louse of pigeons, Lip- 

 eurus baculus. (Na- 

 tural size indicated 

 by line.) 



