A C A R N A A CARDS. 



17 



lin", palpi with the under part of their last joint fur- 

 nished with a moveable appendage. 



Genus ErythrcEW. 



Family IL Gciinmasiihc : Palpi porrect, and simple 



Genus, d 



Family III. Acand<c : Mouth famished with man- 

 dibles, palpi simple, very short, not porrected. 



Genera: Oribil't, Xofftxj/ns, Qcurim, 



B. Mouth furnished with a rostrum. 



Family IV. Lrndl(id<c : Eyes obscure or concealed 



Palpi and rostrum exserted. 



Genus, /.n;./ 



Palpi and rostrum hidden. 



Genus, Uro]io;l(t. 



Family V. Eyes distinct. 



Palpi distinct. 

 'Genera, Clieylctiis, Smarts, Bedcllo. 



Palpi concealed. 



Genus, Snrcoptcs. 



Section II. Legs formed for swimming. 



Family VI. Kiiliiidic: Mouth with mandibles. 



Genus, Ei/Inix. 



Family VII. IJydrarlmula;: Mouth without man- 

 dibles. 



Genera, Hydrachna, Limnochares. 



ACARNA (Linnicus). A genus of herbaceous 

 plants, natives of the south of Europe, belonging to 

 the Linnaean class and order Syngcncsia JEquaKs, 

 Natural order, Composltce. There are only two spe- 

 cies, \\7.. A. gnii!/era, gum-bearing, which is a peren- 

 nial ; and A. canccllata, latticed, which is an annual. 



ACARUS (Linnaeus). A genus of the Annulosa,in 

 the class Acari, and family Acarida: (Leach). Body 

 soft ; mouth naked, and furnished with mandibles, or 

 jaws ; palpi very short, simple, and not porrected : tarsi 

 with a pedmicululed vesicle at their extremities. 



Sp. 1 . A. donie.it ieus. White, with two brown spots ; 

 body ovate, the middle coarctate, with very long 

 hairs : legs equal. It inhabits houses, living in cheese, 

 flour and meal that have been long kept. 



To the naked eye, these minute creatures, the 

 cheese mites, appear little more than moving particles 

 of dust ; but on the application of the microscope 

 they are found to be perfect animals, performing all 

 the regular functions of life. The head is small in 

 proportion to the rest of the body. Their legs are 

 furnished at the extremities with little claws, by 

 which they are enabled to lay firm hold of the sub- 

 stances they inhabit. The body is furnished with long 

 hair-, which enables them to creep through crevices 

 that, would not otherwise admit them. 



The females, which are easily distinguished from 

 the mules, are oviparous. The eggs are so minute 

 that, on a comparative calculation, it appears that 

 ninety millions of them would not fill the shell of a 

 pigeon's egg. These are hatched, in warm weather, 

 in about twelve days; but during the winter season 

 the time of hatching is much longer. When the 

 young first come forth they are extremely minute ; 

 and before they attain their full size they cast 

 their skin several times. 



The mites are very quick-sighted ; and when once 

 they have been touched with a pin, it is easy to per- 

 ceive a great degree of cunnftig exerted to avoid a 

 second touch. They are extremely voracious animals, 

 and are often observed even to devour each other ; 

 and so very tenacious are they of life, that they have 

 been kept alive many months between two concave 



NAT. HIST VOL I. 



glasses, by which they were applied to a microscope. 

 Leeuwenhocck placed a female mite on the point of 

 a pin for examination ; she remained there ten days, 

 and during the time laid two eggs, which for want of 

 food were devoured. 



Arums Scabiei. The acarus that inhabits the vesicles 

 of the itch. 



These insects have also given name to a disease 

 called Acanmia, many curious instances of which are 

 given by medical writers ; and Mouffet relates the 

 following instance of lady Penruddock, concerning 

 whom he expressly tells us, that acari in every part of 

 her body her head, eyes, nose, lips, gums, the soles 

 of her feet, &c. tormented her day and night, till, in 

 spite of ever}' remedy, all the flesh of her body being 

 consumed, she was at length relieved by death from 

 this terrible state of suffering. Mouffet attributes her 

 disease to the acarus scabiei above alluded to; but from 

 the symptoms and fatal result, it seems to have been 

 a different and much more terrific animal. He sup- 

 poses, in this instance, the insect to have been gene- 

 rated by drinking goat's milk too copiously. This, if 

 correct, would lead to a conjecture that it might have 

 been the A. lact'us of Linnaeus. 



Man is not the only animal subjected to the at- 

 tacks of these little tormentors ; from the elephant to 

 the smallest quadruped, from the majestic eagle to the 

 delicate humming bird, from the leviathan of the 

 deep to the smallest fish, all in their turns are annoyed 

 by these minute parasites; and the following well 

 authenticated facts will prove that insects also 

 suffer from them. "The common dung beetles 

 may often be met with in the spring of the year, 

 covered on the underside of the body with small 

 rnites, which look as if they were engaged in 

 suction they are often so numerous that no part is 

 uncovered, they also attack other beetles, especially 

 those of the harpalidre and histipidiae. They are 

 easily disturbed, run with great swiftness, and may 

 often be seen in hot beds, prowling in search of the 

 stercorarious beetles. But the most remarkable 

 insect of this kind is the Urnpoda vcgctans; it 

 derives its nutriment from the insects it assails, 

 not by its mouth, but by means of a long anal 

 pedicle, by which it is attached to them. De Geer 

 round these in such numbers upon a species of leptnra, 

 that its whole body was almost covered with them , 

 they hung from the legs and antennae in bunches, and 

 gave the animal a most hideous and disgusting ap- 

 rauce. Under this load of vermin it could scarcely 

 walk or move, and all its efforts to get rid of them were 

 si vain : many were attached to its body and to each 

 other by their anal pedicles, but others had cast them 

 ff, and \vere walking about. When put into a glass 

 ,vith enrtli, they began to abandon their prey, so that 

 n a few days it was quite free from its plague. He 

 bund that these parasites lived long in alcohol. 



The author of the present article can vouch for the 

 bllowing anecdote, communicated to him by Mr. 

 Daniel Bidder, an indefatigable, well-informed, and 

 old collector of insects, as well as a. close observer 

 of their proceedings. Many years since when col- 

 ecting in the new forest of Hampshire, he sat down 

 >n a bank to take some refreshment, the sun was ob- 

 xeured by clouds, when presently he saw a speciux n 

 of the apis tcrrcst-ris, or humble bee, alight ne: r 

 lint, and begin to scratch, und make a disturli- 

 xnce ; there being no sun the ants had retired, I ut. 

 D 



