FHYLUM ARTHROPODA — CLASS INSECTA 



331 



gers. There are over fifty thousand species of Diptera, ten thou- 

 sand of which are known to occur in the United States. The sub- 

 order Pupipara is a most interesting group, containing the blood- 

 sucking ectoparasites which live upon bats, birds, and mammals. 

 The sheep tick is a fairly common species. 



Order Hymenoptera (Bees, "Wasps, and Ants). — The Hymenoptera 

 are so named because of their membranous wings; the word hymen 

 means membrane. In the winged species there are two pairs of 

 wings, the second pair being smaller than the first pair. The mouth 



Fig. 196. — Flies. Above, Chloropisca glabra Meig. Its maggots feed upon beet 

 root aphids. Below, adult western green-headed horsefly, Tabanits phaenops O. S. 

 (From Knowlton, Rowe, and Madsen, by permission of the Utah Agricultural Ex- 

 periment Station.) 



parts are both biting and sucking, and the females are provided 

 with ovipositors that have become greatly modified. In the ichneu- 

 mon flies, the ovipositor is composed of long slender bristlelike struc- 

 tures, which are used for drilling through the bark of trees and de- 

 positing their eggs upon insect larvae under the bark. The ants, 

 mutillids, and bees use their ovipositors for stinging as well as for 

 depositing eggs. The pigeon horntails bore into trees, causing con- 

 siderable damage. 



