NO. 1382. 



THE ACAlilXA OB .VITES—BAXKS. 



107 



Fumilv DEMODECID.E. 



The abdomen is 



To this family ])elong-s but one genus, Den/odex, found in the se])a- 

 ceous glands and hair-follicles of various mammals, including man. 

 The mite is very small, elongate, with eight short, three-jointed legs, 

 and in front a short, median, sucking rostrun). The palpi are 

 appressed to the under surface of the rostrum, 

 tapering, transversely striate above and below, and 

 rounded at tip. There is a large vulva situate at 

 base of the abdominal venter. The egg is fusiform, 

 and gives birth to a hexapod larva, which moults 

 and becomes octopod. Two more moults brings it 

 to maturity. The nymphs greatly resemble the 

 adults, and the sexes diHer but little. 



]).f(>rilv\dorurii Simon, the species found on man, 

 was long supposed to be the cause of ""blackheads'' 

 and comedomes on the face. Medical authorities 

 claim that the mites do not cause ''blackheads,'' 

 and that they occur in healthy as well as diseased 

 follicles. The mites migrate over the skin to enter 

 new glands. They occur on children as well as 

 adults, and in all parts of the world. 



Z). pliijllo'ides Csokor has l)een found in Canadian 

 swine, causing white tul)ercles on the skin, from the 

 size of a pin-head to that of a pea. Within each 

 of these abscesses a num])er of the Demodc.c were 

 crowded together. They did not appear to affect 

 the health of the animal. I), hovts Stiles was 

 recorded from hides of cattle in the United States. They formed 

 swellings, about the size of a pea. on the skin. AA'ithin each there 

 w^ere a great number of mites. The presence of these tubercles 

 lessens the value of the hide to a considerable degree. Herds could 

 doubtless be cleaned by dipping in some liquid similar to the sheep 

 and cattle dips now in use against other mites. 



Fig. 201.— Demodex 



FOLLICrLORVM. 



LIST OF WORKS USEFl'L IX THE STUDY OF A3IERICAX ACARIXA. 



N. Baxk.s. Some new American Acarina. Trans. Amer. Entom. Soc, XXI, 1S94, 



l)p. 209-222. 

 . On the Ori))atoi(lea of the United States. Trans. Amer. Entom. Soc XXII, 



1S95, pp. 1-18. 



The red Spiders of the United States. Bull. no. S, Teehn. per., Div. Entom., 



U. S. Dept. Agric, 1900, ])p. 65-7: 

 A. Berlese. Acari, Myriopoda et Scorpiones hucusqne in Italia reperta. Pata\'ia, 

 ] S80. [Issued in mixed fascicles; the parts on Prostigmata (Trombidiidit'), Gama- 

 sidie, Oribatidte, and Sarcoptoidea are finished.] 



