212 ECONOMIC ZOOLOGY AND ENTOMOLOGY 



tick carries the parasite of some disease. Their chief impor- 

 tance, indeed, lies in the fact that they are concerned in the 

 transmission of several diseases that are caused by Protozoan 

 parasites. The Texas fever of cattle and the spotted or Rocky 

 Mountain fever of man are the most important of such diseases 

 in America. These will be discussed in Chapter XXVIII. 



The chicken-tick, Argas persicus, is a very serious pest in 

 the southern states. It has a world-wide distribution, and in 

 Persia, where it has habits similar to the bed-bug, it is one of 

 the most dreaded pests, sometimes becoming so numerous 

 that the inhabitants desert the town rather than try to rid it 

 of the pests. 



In Africa the most common tick, Ornithodorus moubata, lives 

 in the huts of the natives and has habits similar to the bed-bug. 

 Besides being a source of great annoyance it transmits a 

 disease known as relapsing fever which has at different times 

 been introduced into the United States, but has not become 

 established here. 



Mites. The mites are much smaller than the ticks, so small 

 that they are not ordinarily seen unless one is searching for 

 them. Yet many of them make their presence destructively 

 or painfully evident, for they are not only important pests 

 of cultivated plants, but they attack man and domestic 

 animals. 



Perhaps the best known of the mites is the "red spider" 

 of the greenhouses, Tetranychus bimaculatus, which is one of 

 the worst pests that occurs in such places. It is found out of 

 doors also and in some regions may totally defoliate almond 

 and prune trees and berry bushes and seriously injure many 

 other plants. These mites do not always have the character- 

 istic red color but during the time that they are feeding they 

 may be light or dark green with dark colored spots. This 

 species passes the winter in the ground. The usual method of 

 control is to dust the trees thoroughly with fine dry sulphur, or 

 the sulphur may be mixed with water, i Ib. to 5 gallons of 

 water, and applied as a spray. The fumes from the sulphur 

 kill the mites. 



Another mite, Bryobia pratensis, also commonly called "red 



