228 PHALANGID.E. ACARID^E, OR MITES. 



irritability for a few moments. The majority of them live upon 

 the ground, upon plants, or at the roots of trees, and are very 



FIG. 450. PHALANGIUM CORNUTUM. 



FlG. 451. GONYLEFTES ACANTHURUS. 



active in their movements ; others hide themselves between stones, 

 or in moss, and are less agile. 



766. The ACARID^E, or Mites, have the mouth formed rather 

 for suction than for mastication ; its various pieces not being sepa- 

 rate, as in the other Arachnida, but more or less enveloped in a 

 sort of sheath formed by a prolongation of the lower lip ; the 

 maxillary palpi, however, are generally free, and their extre- 

 mities are commonly armed by a small pair of pincers. Some 

 of these animals have four or two eyes ; others have only a 

 single one ; and there are several which do not possess any. 

 They are nearly all of very small size, and multiply with great 

 rapidity. Many of them come forth from the egg with only 

 six legs, and may be considered to bear, in this state, a strong 

 resemblance to parasitic insects ; they do not acquire their addi- 

 tional pair until after the first moult, which thus becomes a sort 

 of metamorphosis. The Acaridae are very widely, in fact 

 universally. distributed. Some of them are of wandering 

 habits ; and amongst these, some are found under stones, leaves, 

 the bark of trees, in the ground, the water, or upon various 

 articles of food, such as meat and old dry cheese, and upon putrid 

 animal matters. Others subsist as parasites upon the skin, and 

 in the flesh of different animals ; often greatly weakening them 

 by their excessive multiplication, and producing most violent 

 itching. Other kinds of Mites are parasitic upon Insects ; and 



