ARACHNIDA. 
466 
mined. Each of the four following' segments has a pair of pulmonary sacs and spiracles. Immediately after the 
sixth segment, the abdomen is suddenly narrowed, the six terminal knotted joints forming the tail. The tarsi are 
alike, and 3-jointed, with two terminal ungues. The two nervous cords running from the brain are united at in- 
tervals, forming seven ganglions, of which the tenninal ones belong to the tail. For further details of the anatomy 
of these animals, consult the works of Treviranus, M. de Serres, and L^on Dufour {Journ. de Physique, 1817). 
These Arachnida inhabit the warm countries of both hemispheres, living in the ground, hiding themselves 
under stones or other bodies, generally amongst ruins, or other dark and cool places, and even in the interior of 
houses. They run quickly, and curve the tail over the back. They can turn it in all directions, and employ it as 
an arm of defence or otfence. They seize Wood-lice, and other ground insects, such as Carabi, Weevils Ortho- 
ptera, &c., which serve them as food, with their pincers, pricking them with their stings, and then carrying them 
to their mouth. They are also particularly fond of the eggs of Spiders and other insects. 
The wound occasioned by the sting of the Scorpio europceus is not, as it appears, ordinarily dangerous. That 
of the Scorpion of Souvignargues, of Maupertuis, or of the species which I have named Occitanus, and which is 
more powerful than that of the preceding, produces, according to experiments which Dr, Maccaryhad the courage 
to try upon himself, more alarming elfects. The poison appears to increase in power according to the age of the 
animal. Volatile alkali, either applied interiorly or exteriorly, is used to counteract its elfects. 
Some authors assert that the indigenous [French] species produce two broods in a year, but it appears more 
correct to consider that this takes place in the month of August. According to Maccary, it changes its skin before 
coupling. The female carries her young upon her back for 
several days, at first not quitting her abode at such time, and 
takes care of them for the space of a month, by which time 
they are able to shift for themselves. 
Some have eight eyes, forming Leach’s genus Buthus. 
Scorpio afer, Linn., which is five or six inches long, and in- 
habits the East Indies, Ceylon, &c. S. occitanus, Amoroux, 
(Tunetanus, Herbst.) Middle of Europe, Barbary, Spain, &c. 
The others have only six eyes, forming the restricted genus 
Scorpio of Leach. S. europceus, Linn., Fab., Herbst. South 
of France. 
[The genus Scorpio, Linn., has been revised by Hemprich and Ehrenberg in their great work upon the animals 
of Arabia, and many new genera and subgenera separated therefrom. Many new species have also been recently 
described by Koch, in the continuation of Hahn’s Die Arachniden.l 
Fij;. 32 —Scorpio occitanus. 
THE SECOND ORDER OF ARACHNIDA,— 
TRACHEARI^,— 
Differs from the preceding in the respiratory organs, which consist of radiating or ramified 
tracheiE*, which only receive the air by two spiracles; in the absence of a circulating organ f, 
and in the number of the eyesj, which is only two or four. From the want of sufficiently 
generalized anatomical observations, the limits of this order are not rigorously determined. 
Some species, indeed, of these Arachnida — such as the Fycnogonidcs — do not exhibit any 
spiracles ; and their mode of respiration is unknown. 
The trachean Arachnida are naturally divisible into those provided with chelicerse terminated 
by two fingers, one of which is moveable, or by a single one, equally moveable, in the form of 
a hook, and those where these organs are replaced by simple plates or lancets, which, together 
with the tongue, compose a sucker; but the majority of these animals being minute, their 
examination is attended with very great difficulties, so that these characters ought only to be 
resorted to when it is impossible to adopt others. 
* The tracheffi are vessels which receive and distribute the aerial 
fluid in every part of the interior of the body, and thus remedy the 
want of circulation. They are of two kinds,— tubular or elastic (formed 
of three membranes, the middle one composed of a spiral thread), and 
vesicular, formed of only two membranes these form a kind of pneu- 
matic reservoir, capable of inflation, communicating with each other 
by means of tubular trachere. The tracheae are divided into two prin- 
cipal trunks, extending along the sides of the body, and receiving the 
air by orifices or spiracles. There are also, in many insects, two other 
longitudinal trunks, situated between the preceding, with which they 
communicate, and which Serres calls pulmonary trachem, giving to 
the ordinary ones the name of arterial trachete. He also distinguishes 
the kind of spiracles : the common ones are closed by membranous 
lips, opening by simple contraction the others, named tremaeres by 
Serres, are shut by corneous, moveable plates, and are peculiar to 
.some Orthoptera. Some aquatic larvae have a very peculiar respiratory 
apparatus. 
t The presence of tracheae excludes all complete circulation, — that 
is, the distribution of the blood to different parts, and its return from 
the organs of respiration to the heart. Hence, although certain vessels 
have been discovered in some insects (Phastrue), and their existence 
is possible in the trachean Arachnida, these creatures do not the less 
enter into the general system. M. M. de Serres has observed that the 
intestinal canal of Phalangium emits a very great number of coecums, 
or vermiform appendages, which appear analogous to hepatic vessels, 
and that the tracheae ramify most extensively upon these coecums. 
t According to Muller, Hydrachna urnbrata has six eyes ; but is not 
this a mistake? 
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