CHAPTER XV 

 ARACHNIDS. PROBLEMS OF SPIDERS, MITES, AND TICKS 



Prices would be higher, the demand greater, and the odium attached to 

 ticky cattle at the stockyards removed. Pure-bred Northern cattle could then 

 be brought into the South to improve the native breed, without danger of 

 death from Texas fever ; Southern cattle could enter the show rings of the 

 North without restriction ; and the total cost of tick extermination would 

 be far less than the amount saved in the first year after it had been accom- 

 plished. JOHN R. MOHLER, 1914 



Closely allied to insect problems are those of the arachnids. 

 This group includes scorpions, spiders, mites, and some of the 

 ticks. Interesting as they are, scorpions and spiders are far sur- 

 passed in economic importance by the insignificant mites and 

 ticks. Among the latter are the cattle tick (carrying the germ 

 of Texas fever), the sheep scab mite, mites which attack poultry, 

 and the red spiders and harvest mites which infest vegetation. 



Since arachnids are often mistaken for insects, compare any 

 common insect and spider, noting their similarities and dif- 

 ferences. Make a diagrammatic sketch of each. 



Similarities. Both insects and arachnids are ringed or jointed 

 animals. Both are tracheates, though a few of the arachnids, 

 particularly spiders, have also pulmonary sacs. 



Differences. These will be found in the relation of head 

 and body, the number of legs, presence of antennae, com- 

 parison of palpi. 



* Five species are shown, enlarged and natural size. 1 and 1 a, adult 

 female cattle (Texas-fever) tick ; 2, growth stages and variations in color 

 of this tick ; 3 and 3 a, Rocky Mountain spotted-fever tick, adult female ; 

 4 and 4 a, female dog, or wood, tick ; 5 and 5 a, female European dog tick ; 

 6 and 6 a, female chicken tick. (Reproduced from plates issued by the 

 United States Department of Agriculture and the United States Public 

 Health Service.) 



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