ACARUS FOLLICULORUM. 15 



Acarus folliculorum (Simon, V. Siebold). Pimple mite. 

 (Tab. VIII. figs. 1416.) 



Synonyma: Dernodex folliculorum, Owen; Macrogaster platypus, 

 Miescber ; Simonea folliculorum, Gervais ; Entozoon, afterwards 

 Steazoon folliculorum, Wilson ; Comedonenmilbe. 



According to Von Siebold the name of Acarus is to be retained 

 for it in preference,, as there are also long-tailed Acari, for 

 example, that discovered by Duges in small, pouch-like galls of 

 the leaves of the lime. 



Signa generis. Longit. ~" . Organis generationis omnino ignotis; 

 evolutions imperfectissime cognita. Species vivipara (Wedl). ? 

 Habitat : in capillorum folllculis glandulisque sebaceis humanis et 

 saniset&gre intumidis, imprimis in tola pilis majoribus car ente facie, 

 prceterea etiam in reliquis corporis regionibus, ex. c., in pectore, 

 dor so, fyc. 



According to Schonleiti there is a notice of a mite living in 

 pimples as early as 1682 (' Act. Erudit./ p. 317) ; but according 

 to Schonlein and Remak, the figure given by Bonanni agrees 

 better with the so-called Erdl's mite, or more correctly the bird- 

 mite, which will be hereafter referred to. The true pimple-mite 

 was found by Henle and Gustav Simon in 1842, almost simul- 

 taneously and independently of each other. Henle found them 

 in the hair-follicles of the external ear, but took the tail for the 

 head, and the feet for sucking discs composed of pads. Simon 

 found them in the pustules of acne, and described them correctly. 



With a very variable form the mite is O085 O125'" in length, 

 and 0'020'" in breadth. On the head there are two lateral two- 

 jointed palpi, a tubular proboscis, and a triangular biting organ 

 composed of two fine acute bristles or saws. The head and thorax 

 pass immediately into each other (cephalothoraoe). The short, 

 conical, three-jointed feet are articulated to a chitinous longitu- 

 dinal ridge of the belly by a chitinous stalk, and are, as it were, 

 borne by this stalk, which runs towards the anterior side of the 

 foot, and thence sends a chitinous branch backwards and round 

 the base of the foot. That these horizontal stalks run round the 

 whole anterior part of the body, as Simon thinks, I have never 

 observed, but I think they belong to the base of the foot. The 

 terminal joint of the anterior feet, according to Miescber, has 

 four, that of the hinder feet five processes. Simon describes each 



