276 PuLEx. INSECTS. Arachxida. 
pain, is succeeded by a tickling and not disagreeable sen- 
sation, occasioned by the insect sucking its sanguineous 
draught. The female lays a number of oval eggs of 
pure white colour, selecting frequently a hearth-rug, 
carpet, or chair cushion ; at other times she deposits 
them in dusty cracks in the floor. The larvae are long 
slender thread-like worms which, when full grown, spin 
and inclose themselves in silken cocoons. 
The species that attacks man is the Pulex irritans, 
a figure of which is given on Plate 11, figs. 15, 16, 
Although sufficiently numerous in this country, parti- 
cularly in dirty houses and amongst people of dirty 
habits, little idea of the multitudinous hosts in which 
they swarm in hotter parts of the globe can be formed, 
until the traveller makes their acquaintance in favoured 
localities. We have been told that they skip about in 
the streets of Naples by thousands ; on the shores of 
its lovely bay they assemble in myriads; and in all con- 
tinental churches they abound, particularly under the 
dome of the magnificent church of St. Peter at Rome. 
A particular and distinct species attacks the dog, but 
the same species is found on the cat, and it freely 
attacks man himself. This is the Pulex canis. 
A distinct species is found on the cat, and ho doubt 
were the subject pursued, many distinct species exist 
attached to different animals. A much more formi- 
dable insect than the flea is found in the West Indies, 
popularly known in those latitudes as the Chigoe 
(Sarcopsylla penetrans), Plate 11, figs. 11, 12. Mr. 
Waterton in his “ Wanderings” says, “ It looks exactly 
like a small flea, and a stranger would take it for one ; 
it attacks different parts of the body, but chiefly the 
feet, betwixt the toe nails and the flesh. There it 
buries itself, and at first causes an itching not unplea- 
sant. In a day or two you perceive a place about the 
size of a pea, somewhat discoloured ; this is the nest 
of the Chigoe, containing a hundred eggs, and if 
allowed to hatch there the young ones will soon begin 
to form other nests, and in time cause a spreading 
ulcer. As soon as you perceive that you have got a 
chigoe in your flesh, with a sharp-pointed needle or knife 
you must take it out.” Neglect of the latter precaution 
is followed by moat serious results. It would appear 
that the attack of this insect on persons of inflammatory 
habit, has frequently been followed by fever and great 
suffering and pain. 
Class— AKACHNIDA. 
This class of articulated animals contains the spiders, 
scorpions, and mites ; the spiders forming the order 
Araneidea. A concise summary of their organization 
and economy is all that our limited space will allow. 
In spiders no distinct head, as in insects, will be 
observed ; it is, as it were, merged into and apparently 
forms a part of the thorax, hence called the cephalo- 
thorax, the head and thorax being continuous ; there 
are few exceptions to this rule. Spiders have no 
antennse, and nearly all have eight legs ; a few have 
six, and others ten. On the anterior, or cephalic portion 
of the thorax, are situated the eyes; these are eight, six, 
or two in number. Those organs which are used for 
seizing, and which in insects would be called mandibles, 
are in spiders called falces; these are situated in front, 
and are usually terminated by a sharp hook or fang. 
Tiie legs are eight-jointed, having two or more claws 
at their apex. Their abdomen is soft, usually globular, 
but in some species oblong ; it is in one piece, never 
having segments as in insects ; at its apex beneath are 
six or eight fleshy mammulse or spiracles ; it is from 
these that the silk issues, when the animal is spintiing. 
All spiders have eyes; they are smooth, and as observed 
above, differ in number ; they also differ much in size 
and position, and from this circumstance important char- 
acters for their systematic arrangement are derived. 
The falces, although modified in form in different 
species, are usually subconical, having at the extremity 
within, a longitudinal groove, the sides of which are 
dentate ; this groove receives the fang when in repose. 
The claw or fang is hard, and acute at the point, near 
to which is a small opening which emits a colourless 
fluid ; this, in some species, appears to be of a poisonous 
nature. 
The falces are the organs in spiders which are used 
to seize and hold their prey. Spiders are extremely 
voracious, but are capable of enduring the want of food 
for a very long period ; some species have been known 
to live from six to eight months without nutriment. 
In no animal apparently is tlie sense of touch so fine as 
in the spider ; and on this sense much more than on sight, 
do many species depend for ascertaining the presence 
of insects, upon which they prey. The poet has finely 
described the sense of touch in spiders, which he says, 
“ lies in each thread, and lives along the line.” The 
accuracy of this description may be proved by any one 
who will notice a species of spider that spreads its 
geometric net on plants, from which many lines will be 
seen to converge to the mouth of its den ; this will be 
in some hole in an old wall, &c. No sooner does an 
insect touch any part of the net, or of the silken cords 
that retain it in its position, than the spider through the 
delicacy of his sense of touch becomes instantly aware 
of its presence ; the garden spider, Epeiva diadema, 
may always be tempted out of its hiding-place by 
touching its web lightly with a twig or straw, — Fig. 177. 
Spiders have been ascertained to undergo several 
moultings, subsequently to the time when thej' first escape 
from the egg, and before they arrive at maturity; some 
have been known to moult five, others as many as nine 
times. They also possess the power of reproducing limbs 
that have become mutilated, or which they have alto- 
gether lost; but this capability does not appear to have 
been observed in such as have arrived at maturity. 
Any account of the economy of spiders, approaching 
even a satisfactory sketch of their history, would occupy 
a bulky volume; a few general observations is all that 
can here be attempted. Some species burrow, or 
excavate dens or holes in the ground ; these are of a 
cylindrical shape, and are lined with a thick tissue of 
