PHYLUM ARTHROPODA 



381 



Fig. 322, continued. — Order Acarina. C, follicle mite, Demodex folliculorum. 

 D, itch-mite, Sarcoptes scabiei. E, sheep-scab mite, Psoroptes communis var. 

 ovis (A, B, E, from Osborn ; B, after Packard; C, D, from Sedgwick's Zoology ; 

 C, after Megnin, D, after Gudden.) 



ticks is the transference of a sporozoan parasite, Piroplasma 

 bigeminum, from. the blood of one animal to that of another. 

 This parasite produces Texas fever, a disease that causes an 

 annual loss of about $100,000,000 in the United States. 



Other members of the order Acarina that should be men- 

 tioned are: (1) the follicle mites, Demodex folliculorum (Fig. 322, 

 C), that lives in the sweat-glands and hair follicles of man and 

 some domestic animals, causing what are known as "black- 

 heads " ; (2) the itch-mite, 

 Sarcoptes scabiei (Fig. 322, D) 

 which burrows beneath the 

 epidermis of man and causes 

 intense itching; and (3) the 

 scab parasite, Psoroptes com- 

 munis (Fig. 322, E), which 

 feeds on the skin of sheep, 

 cattle, and horses, producing 



scabs. Fig. 323. — Order Pedipalpi. A 



r\„i -r, «• , • /t^ South American species, Admetus 



Order 5. Pedipalpi (Fig. pumiUo Gft> ^^ leg; Kt pedi . 



323). — The members of this palpi. (From Sedgwick's Zoology.) 



