COLLECTION AND PRESERVATION OF INSECTS 33 



These insects are commonly found on domestic animals but not on 

 fowls. The human louse, or "cootie," belongs to this order. They 

 feed by sucking blood and are frequently important pests of domestic 

 animals and man. The common cootie, or body louse of man, trans- 

 mits the dread typhus fever, a disease which may become especially 

 serious in time of war. 



THYSANOPTERA 



Thysanoptera (thrips) are mostly very small insects, usually with 

 two pairs of slender wings with few veins but fringed with long 

 hairs ; the legs and antennae are short. The mouth parts are formed 

 for piercing and sucking, and the immature stages resemble the adults. 

 (See fig. 24.) Some of these insects feed on plants; others are preda- 

 ceous.on small insects. Those that feed on plants are frequently very 

 injurious in greenhouses or on truck crops. 



Figube 24. — Thysanoptera. The flower thrips (Frankliniella tritici (Fitch)), a 

 common species. Actual length about 1 mm. 



HEMIPTERA 



Hemiptera (true bugs, cicadas, leaf hoppers, aphids, scale insects, 

 and their allies) are either winged or wingless, the winged members 

 having two pairs of wings, the front pair frequently somewhat thick- 

 ened, the hind pair membranous. The mouth parts are formed for 

 piercing and sucking. The immature stages resemble the adults. ( See 

 figs. 25, 26, 27, and 28.) Most members of this order feed on plant 

 juices, but some are predaceous on other insects, and some, such as 

 the bedbug, suck blood from animals or man. Most forms are terres- 

 trial, but some are aquatic. The plant-feeding forms include some 

 species like the chinch bug and some scale insects that cause a great 

 deal of damage to crops; other species are known to transmit virus 

 diseases of plants. 



