ACANTIIOPUS 4 ] 



BIBL. Miiller, Ber. d, Berl. Ak. 1855, 

 p. 248 ; id. Abh. d. Berl. Ak. 1858, p. 1 ; 

 Hfickel, Radiolar., 1862; Claparede and 

 Lachmann, In fits. p. 59. 



ACAN'THOPUS, Vernet. A genus of 

 Entomostraca, Ord. Ostracoda, fam. Cythe- 

 ridse. Lake of Geneva. 



BIBL. Bibl. Univ. 1877 (Jn. Mic. Soc. 

 1878, p. 80). 



ACA'REA. A family of Arachnida, be- 

 longing to the order Acarina (ARACH- 



ACARUS. 



These animals are commonly called mites ; 

 and every one is familiar with them as oc- 

 curring in cheese, sugar, flour, &c. Some 

 also occur upon the skin of man and 

 animals, producing the itch and the 

 mange. 



The parts of the mouth and the legs, upon 

 which the characters are usually founded, 

 may be best made out by crushing the ani- 

 mill upon a slide with a thin glass cover, 

 and washing away the exuding substance 

 with water, as directed in the Article PRE- 

 PARATION ; sometimes hot solution of pot- 

 ash is requisite, with the subsequent addi- 

 tion of acetic acid and further washing. 

 When afterwards dried and immersed in 

 Canada balsam, the various parts become 

 beautifully distinct, and may be perma- 

 nently preserved. 



Acarus (Tyroylyph'us), Body with a 

 transverse furrow between the 2nd and 3rd 

 pairs of legs ; legs nearly equal, all perfect, 

 and terminated by a membranous sucker or 

 claws, or both ; palpi adherent to the la- 

 bium (or lip). 



Hypodera*. Body very long, legs very 

 short, and the 2 anterior and posterior pairs 

 far apart; parasitic beneath the skins of 

 birds. 



Hypopus. Front pair of legs mostly 

 largely developed ; posterior almost atro- 

 phied. Parasitic on animals and plants. 



Trichodactylus. Rostrum (beak) short, 

 with minute bristles ; 4th pair of legs longer 

 than the rest, without claws, and terminated 

 by a very long bristle, the rest with 2 claws. 

 (Parasitic on Bees.) 



Psoroptes. Body soft, depressed, spiny 

 beneath and at the base of the legs ; poste- 

 rior pair of legs small and rudimentary, the 

 rest with a claw and sucker ; body termi- 

 nated by two bristly projections. (Para- 

 sitic on the Horse.) 



Sar copies. Body soft, transversely wrin- 

 kled, and with dorsal papillae ; anterior 

 2 pairs of legs with suckers, posterior ter- 



minated by a long bristle, and without 

 suckers. (Parasitic.) 



Demodex. Body elongate ; cephalothorax 

 distinct from the ringed abdomen : legs 

 terminated by 4 or 5 very minute claws. 



ACAREL'LA, Kent. A genus of In- 

 fusoria ; near Halteria. Kent, Man. Inf. 

 1880, p. 214. 



AOAREL'LUS, Westwood. A sup- 

 posed genus of Acarina. See HYPOPUS and 

 PHYTOPTIDA. 



They seem to consist of larvae of Phy- 

 topti or species of Hypopus. 



BIBL. Westwood, Proc. Entom. Soc. 18C4, 

 p. 30, and 1870, p. 30 ; Tatem, Mon. Mic. Jn. 

 1872, viii. p. 263 ; Murray, Econ. Entmnol. 

 p. 246; Mclntire, M. Mic. Jn. 1874, xi. p. 1. 



AOARI'NA. An order of ARACHNIDA. 



AC'ARUS, Linn. (Tyroglyphus). A 

 genus of Arachnida, of the Order Acarina, 

 and family Acarea (see ARACHNIDA and 

 ACAREA). 



The palpi adherent to the labium, the 

 perfect legs, and the transverse furrow dis- 

 tinguish the genus. 



Ac. domesticus, or siro (PI. 6. fig. 1), the 

 common Cheese-mite. Body oval, soft, 

 whitish, turgid and furnished with long 

 feathery hairs (6). The transverse furrow 

 (c) occurs at about the anterior fourth of 

 the body ; and another is seen between the 

 head and the part corresponding to the 

 thorax. The head is susceptible of elevation 

 and depression. In its natural state it 

 appears conical (d}, and is furnished with 

 two large mandibles ; these consist of a soft 

 retractile basal joint (e), and a second, di- 

 lated, non-retractile joint (/) resembling 

 the fixed claw of a lobster, and a moveable 



Eiece (/*) working against the latter. The 

 ist two pieces are toothed where in contact 

 with each other. These mandibles can be 

 advanced separately or together, and be 

 separated or approximated. When in a 

 state of repose, they form as it were a roof 

 above the labium. The labium (g) is quadri- 

 lateral, elongated, notched at the end, thin 

 anteriorly and in the middle, and consolida- 

 ted laterally with the palpi, which are 4- or 

 5-jointed (h h). The legs are reddish, in- 

 serted in two separate groups, but not very 

 far distant as in Sar copies. The anterior 

 pair of legs are remarkable for their size in 

 the male, which is smaller and more active 

 than the female ; the third pair are the 

 shortest and smallest ; the third joint or 

 femur is larger and longer than those next 

 it; the sixth joint is long and thin; the 



