PHYLUM ARTHROPODA 



381 



E 



FIG. 322, continued. Order ACARINA. C, follicle mite, Demodex folliculorum. 

 D, itch-mite, Sarcoptcs scabiei. E, sheep-scab mite, I'soraptcs commitnis var. 

 oms (A, B, E, from Osborn ; B, after Packard; C. D, from Scd^wick'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: (i) 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 coin- 

 munis (Fig. 322, E), which 

 feeds on the skin of sheep, 

 cattle, and horses, producing 



scabs. FIG. 323. Order PEDIPALPI. A 



/-\ T-> i i - /!-< South American specie?, Adtnetus 



Order ^ Pedioaloi (ri' 



<J puiiiilio. Go, anterior leg; A/, pedi- 



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



