Chap. 30 ARTHROPODS INSECTS, SPIDERS, AND ALLIES 629 



It will drop off when surfeited with blood. The danger from ticks is in the 

 organisms they may carry from an infected animal to an uninfected one. Some 

 of the resultant diseases are: relapsing fevers of certain western states, due to 

 a species of spirochaete; RocTcy Mountain spotted fever of rodents and man 

 caused by Rickettsia organisms; and tularemia, a disease of rabbits, squirrels, 

 rats and certain game birds, caused by a bacterium {Pastiirella tularemia) 

 carried by the tick {Dermacentor andersoni) . Tularemia is highly infectious 

 to man since the organisms pass through slight breaks in the skin when infected 

 game is handled. 



Mites live on plants and animals and cause great damage to both. Among 

 those of plants are the destructive stored grain mites, the citrus bud mite of 

 the lemon trees of California, the mites on peas, clover, and the "red spiders" 

 of junipers (Fig. 30.34). The parasitic mites of animals include the "southern 

 chiggers" or "red bugs" whose larvae burrow just under the skin as a ground 

 mole burrows just under the surface of a lawn. 



