260 



COLLEGE ZOOLOGY 



Stomach. The cattle grubs of the ox warble 

 fly (Fig. 158) cut holes in the skin of cattle 

 and damage the hide; the animals also lose 

 flesh. 



Household insect pests 



Insects that are unwelcome guests in the 

 house (Fig. 159) are sometimes only annoy- 

 ing, but they may become destructive. Food 

 may be spoiled by cockroaches, ants, fruit 

 flies, and weevils; clothing, carpets, furs, and 

 feathers may be injured by clothes moths 

 and carpet beetles. Among the piercing in- 

 sects that are annoying are stable flies, bed- 

 bugs, and mosquitoes. 



Chemical control of household insect 

 pests involves the use of chemicals that kill 

 or repel them. 



Insects that transmit 

 human diseases 



No doubt insects that carry diseases (Fig. 

 160) are one of the greatest enemies of man 

 and affect human welfare most profoundly. 

 Some of the more important species are the 

 house flies that spread the bacteria of ty- 

 phoid and of summer diarrhea; mosquitoes 

 that transmit malaria, yellow fever, dengue, 

 and filariasis; fleas that convey the bacteria 

 of bubonic plague from rat or ground 

 squirrel to man; body lice (cooties) that are 

 responsible for transmission of t\phus fever; 

 and tsetse flies that are the vectors of Afri- 

 can sleeping sickness in man, and nagana 

 and other diseases in domestic animals. 



Our federal and state governments and 

 educational institutions all recognize the 

 necessity of controlling injurious insects, and 

 hence economic entomology has become 

 one of the most important activities in the 

 scientific field, both pure and applied. De- 

 partments of health devote a considerable 

 part of their funds and efforts to the subject 

 of insect control, especially the control of 

 house flies and mosquitoes. 



CLASSIFICATION OF 

 THE INSECTS 



{For reference purposes only) 



Insects are divided into orders principally 

 on the basis of the following characteristics: 

 ( 1 ) with or without metamorphosis; if meta- 

 morphosis occurs, whether gradual, incomplete, 

 or complete; ( 2 ) type of mouth parts, and ( 3 ) 

 number and type of wings. Minor features are 

 also of service. Some of the entomologists di- 

 vide a few of the orders listed below still 

 further, but to simplify we are giving only 25 

 as follows: 



1. Protura. 



2. Thysanura. Bristletails, etc. 



3. Collembola. Springtails 



4. Orthoptera. Grasshoppers, etc. 



5. Isoptera. Termites 



6. Neuroptera. Aphislions, etc. 



7. Ephemeroptera. Mayflies. 



8. Odonata. Dragonflies 



9. Plecoptera. Stoneflies 



10. Corrodentia. Booklice, etc. 



1 1 . Mallophaga. Bird and other biting lice 



12. Embioptera. Embiids 



13. Thysanoptera. Thrips 



14. Anoplura. Sucking lice 



1 5. Hemiptera. Bugs 



16. Homoptera. Plant lice, etc. 



17. Dermaptera. Earwigs 



18. Coleoptera. Beetles 



19. Strepsiptera. Stylopids 



20. Mecoptera. Scorpionflies and others 



21. Trichoptera. Caddisflies 



22. Lepidoptera. Moths and butterflies 

 25. Diptera. Flies 



24. Siphonaptera. Fleas 



25. Hymenoptera. Bees, wasps, ants, etc. 



Order 1. Protura (Or. proto, first; uro, 

 tail). Primitive; wingless; no metamorphosis; 

 mouth parts insectlike; without antennae or 

 true eyes; abdomen of 12 segments; live in 

 damp places; about 30 species. Ex. Acerentulus 

 barberi. 



Order 2. Thysanura (Or. thysanos, tassel). 

 Firebrat (Fig. 129). Primitive, wingless; no 

 metamorphosis; chewing mouth parts; 11 ab- 



