ACARINA PARASITES. 457 



in the moment of danger it quickly draws in its head and 

 feet, somewhat resembling the tortoise ; its march is pre- 

 cisely that of the tortoise. It usually lays sixteen eggs, 

 which are carefully deposited in furrows under the skin, and 

 ranged in pairs ; these are hatched in about ten days. 



No. 4, fig. 220, Demodex folliculorum, is another very 

 remarkable parasite found beneath the skin of man, and 

 may be obtained from a spot where the sebaceous follicles, 

 or fat glands, are abundant ; such as the forehead, the 

 side of the nose, and the angles between the nose and 

 lip ; if the part where a little black spot or a pustule is 

 seen, be squeezed rather hard, the oily matter there accu- 

 mulated will be forced out in a globular form ; if this is 

 laid on a glass-slide, and a small quantity of oil added to 

 it, to cause the separation of the harder portions, the little 

 insect, in all probability, will float out ; after the addition of 

 more oil, it can then be taken away from the oily matter by 

 means of a fine-pointed sable pencil-brush, and transferred 

 to a clean slide ; when dry, it should be immersed in 

 Canada balsam, and covered over with thin glass, that is 

 mounted in the usual way. 



The Cheese-mite, Acarus domesticus (fig. 220, No. 2), has 

 a peculiar elongation of its snout, forming strong, cutting, 

 dart-shaped mandibles ; these can be advanced separately 

 or together, being tooth-like when in contact. Mites 

 multiply very rapidly ; they are both viviparous and ovi- 

 parous ; the eggs are hatched in about eight days ; if de- 

 prived of food, they kill and eat each other very greedily. 

 Acarea infest almost the whole of our dried articles of 

 food. Ac. passerinus has two very long buccal bristles; 

 it lives upon dried figs, and other saccharine fruits. 

 Ac. destructor has long black hairs; it feeds upon the 

 contents of entomological cabinets, especially butterflies ; 

 Ac. hippopodos is found upon the crusts of ulcers on 

 horses' and sheep's feet. The various parts, as the mouth 

 and legs, of acari will be best made out by crushing the 

 animal upon a glass slide, with a thin glass cover ; then 

 wash away the exuded substance with water sometimes 

 a hot solution of potash is requisite, with a subsequent 

 addition of acetic acid and washing ; after drying, mount 

 them in Canada balsam. 



