470 Div. 3. ARTICULATA.— ARACHNID A. Class 2. 



terminated in various ways, according to tlieir habits. Some of these insects {Acarides, Latr.) have 

 eight legs, fit only for walking, and chelicerae. 



Tromfi/rf/MW, Fabr., has the chelicerae terminHted by a moveable daw; palpi projecting:, pointed at tip, with a 

 moveable appendag^e or fing-er beneath tlie extremity; t'.vo cni s, each at the top of a small fixed peduncle. T. Uolo- 

 gericeiim, Fabr., very common in {rardens durinir sprin:.', of a blood-red colour, with tlie abdomen nearly 

 square, and narrowed behind. A nuicli larsfor species ('/'. citirloriiim, Fabr.) inhabits the East Indies, and emits a 

 red dye. 



En/Z/ineus, Latr., has the chelicerae and palpi of Trombiiliiim, but the eyes are sessile, and the body not divided. 

 E. phatangioidvs, Latr. 



Gmnasus, Latr., iias the cheliceric didactyle, and the p.ilpi projectni';, distinct, and tiliforni. In some, the body 

 is covered entirely, or in part, by a scaly skin, but in others it is entirely soft. Some of the latter siiecies live upon 

 different birds and quadrupeds. Others, as the Aainis h-lniiiis, Linn, [or the Red Spider of the hot-houses], form, 

 upon the leaves of various ve>:etables, esiiecially uikhi those of lime-trees, very tine «ebs, which injure them greatly. 

 This species is reddish, with a black spot on each side of the abdomen. 



Clieyleius, Latr., has didactyle chelicera ; but the palpi are thick, arm-like, ami terminated by a sickle-shaped 

 joint. A. enalitus, Schr. 



Oribata, Latr. (Notaxpis, Henn.), has the chelicer.-v also didactyle ; the palpi very nIkuI, or concealed ; the body 

 covered with a hairy, scaly skin ; feet Ion,', or moderate. The front of the body is advanced like a beak. Found 

 upon stones, trees, in moss, &c. They creep but slowly. 



Uropoda, Latr., has, from analogy, forceps-like chelicera' ; palpi not pr.ni ctin<j; body covered with a scaly skin; 

 legs short ; anus with a long thread, by which this insect is attached to vin ious beetles, and suspended in the air. 

 A. vegetans, De Geer. 



Acarus, Fabr. (Sarropics, Latr.), has two ilidactyle chelicersc ; palpi very short, or con- 

 cealed ; body very soft ; tarsi terminated by a vesicle. Some species feed upon our ali- 

 mentary substances (./. iIoiihwUciix, A. fariiiw); others are fouiul iu the ulcers of the itch 

 in man, tlie horse, cat, dog, &c. (A. xcal/iei. See theThesis of Ur. (Jalet upon this species). 



Other Mites or Ticks (Ricixi.e, Latr.) have also eight legs, formed for walking, 

 „ „ but destitute of cheliccrie, wliicli are replaced bv lancets, forming, with the tongue, 



mngiiified. a sucker. Some have the eyes distinct. 



Bdella, Latr., having the sucker advanced and beak-like, with long, elbowed palpi, and four eyes. Scinit longi. 

 rostris, l\mn. 

 Smaridia, Latr., with palpi short and straight, and two eyes. A. sambuci, Schr., &c. 



The other Ricinijc have not the eyes perceptible ; the palpi are in the shape of valves, dilated at the 

 ti]), serving as a sheath to the sucker, of whjcli tlie jiarts are horny and toothed ; the body is clothed 

 with a corneous skin, or at least with a scaly plate in front. These ticks are parasites, sucking the 

 blood of various vertebrated animals ; and altliongh at first very much flattened, they acquire, by suc- 

 tion, a very large size, and become swollen out like a bladder. Tliey are round or oval. 



Ixodes, Latr. (Ci/nor/ncs/fs, Hcrm.), has the palpi casing the sucker, and forming, with it, a pro- 

 jecting beak, truncated, and slightly dilated at the tip. They are found in thick woods, abounding 

 in bru.sh-wood, briers, &c., attaching themselves to low plants by the two fore-legs, extending the 

 other feet. They fasten upon dogs, cows, horses, and other quadrupeds, and even upon the tortoise, 

 burying their suckers so completely in their flesh that they can hardly be detached by force, and by 

 tearing a»ay the ixirtion of skin to w l.icli they are fastened. They deposit a prodigious number of 

 eg)fs, discharging them from the mouth, according to M. Chabrier.* Tlieir multiplication iqion the 

 ox and horse is sometimes so great that these animals perish from exhaustion. The tarsi arc termi- 

 nated by two ungues inserted upon a plate, or are united at the base upon a common peduncle. The 

 ancients appear to have known these animals under the name of Ricini. They are our well-known 

 Ticks, — Ixodes rirhius, Linn., attacking the Dog; and Lr. reticiilaiiis, Latr., Fabr. {Acarus redxviiis, piuiul>7u^,"and 

 Schr.), the Ox. The latter, when swollen, is half an inch long. The study of the species of this genus lljV'li"'*' '""'' 

 is not sufficiently advanced. 



Arijax, Latr. (li/ii/nc/ioprioii, Ilerm.), differs from Lxodes in the inferior situation of the mouth, and the palpi 

 not encasing the sucker, and being 4-jointcd instead of three. A. reflexus, Fabr., Latr. Upon i)igeoiis. A. persiais 

 (Malleh de Mianeli), described by travellers under the name of the Venomous Bug of Miatia, has been the subject 

 of a curious memoir by M. Fischer de AValldheiin. [This insect formed the subject of much discussion at the 

 Liverpool meeting of the Hritish Association]. 



[.NL Audouin has described and figured some species of the two preceding genera, and of those of Tetranyclma 

 and Pteroptus, in the Annates des Sci. Nat. for 1832.] 



Other Mites {Hydrachnellce, Latr.) have also eight legs, hut theyare ciliated, and fitted for swimming. 

 They form the genus Hgdrachna of Miiller (.r^/ajr, Fabr.), and live only in the water. The body is oval 



* [The aiiitt orifice betni; minute, .iiid cM»c to liie mouth, lins been niist.'iken for the iaticr in this ubservatioti.] 



