DEMODEX FOLLICULORUM 695 



body. The suckers are broad and carried at the end of a short simple 

 pedicel. The male has copulatory suckers and abdominal projections. 



This genus contains two species, Chorioptes symbiotes, Verh., which 

 lives in colonies among the scabs it produces by its bites, and Chorioptes 

 cynotis, Hering, which lives in the concha of the dog, cat and ferret. 



FAMILY ERIOPHYIDAE 



This family contains a large number of minute acari of peculiar form 

 which live on plants and cause galls, differing from those made by 

 insects, in that there is an opening through which the acari can pass. 

 The adult has only two pairs of legs, situated at the anterior end of the 

 body ; the posterior pairs are wanting, and appear to be represented by 

 long delicate hairs ; they have no respiratory organs and are thus 

 placed in the group Zemiostigmata. They cause considerable damage to 

 useful plants. 



FAMILY DEMODICIDAE 



This family contains the sebacic mites, which belong to the single 

 genus Demodex ; the species are parasitic in the sebaceous glands 

 and hair follicles of man and animals. They are extremely small, 

 have elongated transparent bodies with eight short mole-like legs. The 

 rostrum is short and trapezoidal in shape ; the mandibles and maxillae 

 are styliform, and the palps are closely applied on the lower surface of 

 the rostrum. The abdomen tapers to the posterior end, which is rounded 

 and transversely striated above and below ; the legs are short and con- 

 sist of three joints ; respiratory organs are wanting. The egg is fusi- 

 form in shape and there are one larval and two nymphal stages, the latter 

 closely resembling the adults. 



Demodex folliculorum, Simon, is parasitic in the sebaceous glands of 

 man. The female measures '38 mm. in length and the male '30 mm. 



Demodex canis, Tulk. This species is regarded as a variety of 

 folliculorum, and, as its name implies, is parasitic on the dog ; it is, however, 

 smaller, the female measuring '25mm. in length and the male '22 mm. It 

 produces little swellings in the skin which become pustular and cause 

 intense itching ; these swellings are usually full of the mites and when 

 there are a large number of them the animal emaciates and may event- 

 ually die. 



Demodex phylloides, Caskor, is an allied species which lives in the 

 skin of swine and causes small w r hite tubercles. The animals do not 

 appear to be affected by it. 



