PHYLUM ARTHROPODA — CLASS INSECTA 



333 



ants, honey bees, and social wasps are examples. The Hymenoptera 

 found in this country are divided into three suborders, twenty- 

 eight families and about twelve thousand species. The honey bees 

 and silkworms are the only really domesticated insects. 



Other Orders 



Other orders than the ones discussed above are included in the 

 notable treatises on entomology. These are in the main, however, 

 rare and little known insects. Professor Comstock in his An Intro- 

 duction to Entomology, recognizes twenty-five orders : the Zoraptera, 

 insects resembling termites in many respects, and consisting of but 



Fig-. 198. — The common wasp, or yellow-jacket, Vespula pennsylvamca Saussure. 

 (Prom Sorensen and Knowlton, by permission of the Utah Agricultural Experiment 

 Station.) 



six known species in a single genus Zorotypus; the Corrodentia, 

 psocids and book lice; the Mallophaga, wingless ectoparasites of 

 birds; the Embiidina, a small group of about seventy species found 

 in the warmer parts of the world, living under stones and in the 

 detritus of the soil; the Anoplura, the true lice, an order consisting 

 of sixty-five species of blood-sucking parasites found on the mam- 

 mals; the Strepsiptera, a group of small twisted- winged insects that 

 live as parasites within the body of other insects ; and the Mecoptera, 

 a group of about forty American species, commonly called scorpion 

 flies, in addition to the eighteen orders discussed above. Brues and 

 Melander in their Classification of Insects recognize thirty-four or- 



