Encyclopaedia Britannica, or, a Dictionary of arts, sciences, and miscellaneous literature : enlarged and improved. Illustrated with nearly six hundred engravings > Volume 8, ELE-FOR

234
ENTOMOLOGY.
Ge j'-ral pain, inflammation, and fwelling, -which follow a wound
tbiir- infliaed bythefe
t In the fcorpion, there is a fluid of a very malignant
nature, which the animal difcharges at pleafure through
its fling ; under certain circumftances, this fluid pro¬
duces fatal effects. Some of the fpiders difcharge a fluid,
which renders their bite dangerous. The aranea avicu
/aria, and the tarantula, in particular, are well known;
even the common fpiders inflidt a fatal wound on the
infedts they entangle in their web. The filk of the
common filk-worm and other caterpillars, according to
Malpighi, Lyonnet, and others, is a fluid contained in
two veflels, which are of a confiderable fize at the ex¬
tremity, and taper towards the mouth, and become very
flender.
The carabus and dytifcus contain an acid which
reddens the infufion of litmus. The ant contains an acid
well known to chemifts.
The acrid matter contained in the body of the lytta
vejicatoria, is ufed in medicine, and forms the bed
epifpaftic we are acquainted with.
Generation of InfeEls.
Insects are the only animals without vertebrae in
which the fexes are diflinguithed. Copulation is per¬
formed in them by the introduftion of the parts of ge¬
neration of the male into thofe of the female.
All infeils are either male or female, except in a few
of the genera of the order Hymenoptera, (fuch as the
. bee, ant, &c.) where individuals are to be found, which
are neither male nor female; and, on that account call-
«d neuters. Among the bees, the neuters form the far
greater part of the community, and perform the office
of labourers. Among the ants, the neuters are very
numerous, and conftitute the. only active members of
the fociety. It has been alleged that thefe neuters are
nothing but females, whofe parts have not been deve¬
loped for want of proper nouriffiment. Olivier, how¬
ever, after ftridt examination, is difpofed to think them
really different, though he does not adduce fads fuffi-
eient to eftabliffi his opinion.
The parts which di inguifli the male from the
female, may be divided into two claffes, viz. i. Thofe
which are not directly connected with generation. 2.
Thofe which are abfolutely neceffary for the purpofes
of generation. The circumftances which have no direct
communication with generation, which ferve to point
out the diftin£tion between the fexes, are, I. The dif¬
ference of fize, obfervable in the male and female.
1. The brightnefs of the colour in each. 3. The form
and number of articulations of the antennae. 4. The
fize and form of their wings. 5. The prefence or abfence
,of a fling. The male is always fmaller than the female.
The female am is nearly fix times larger than the
male. The female cochineal is from 1 2 to 15 times
the fize of the male. The f m 1e tertnes is '’OO or ^00
times the fize of the male. The colours of the male
are commonly much more brilliant than thofe of the
female; this is particularly the cafe in lepidopterous in¬
fects. In fome infefts, the colour of the male is totally
different from that of the f male. The antennae of the
male are commonly of a different form, and larger than
thofe of the female. Frequently the males are furnifti-
ed with wings, while the females have none j the
2
latnpyris, coccus, and blatta, and feveral moths, afford General
an example of this. The female bee is furnilhed with 0bfcrva,
a fling, while the male is deftitute of one. The males tlOI,s•
of fome infefls are furniffied with fharp prominent '
points, refembling horns, lituated either on the head or
breaft, which are either not perceptible, or very faintly
marked in the female. The parts effential to gene¬
ration.afford the heft diftinguifhing mark. In moft in¬
fers they are fituated near the extremity of the redlum.
By prefling the abdomen near to the anus they may
frequently be made to protrude. But the parts of ge¬
neration are not always fituated near the anus. In the
fpiders they are fituated in the feelers. In the tibel-
lula, the male organ is fituated in the breaft, while,
that of the female is placed at the anus..
Organs of Generation.
In male infefls, the organs which ferve for the pre¬
paration of the femen, bear fome refemblance to thofe.
organs in the animals which compofe the clafs Mam-
tnaha. All of them have four organs, two of which
may be compared to the tefticles, and the other two to
the veficulee feminales. They vary very much in form
in different fpecies. During the period the male is
ufually employed in impregnating the female, thefe
parts are very diftinft ; after that, they difappear total¬
ly. In the larger aquatic infefts, (particularly in the
hydrophilusj befides thefe four organs already mention¬
ed, there are other two fmall velicles which may be
compared to the proftate gland of the fuperior ani¬
mals. The vafa deferentia in the hydrophilus are fome-
what reflected, its tefticles are very large, and terminate
in a very fiender folded filament. In the graihopper,.
thefe four organs are likewife found, but the vejicu/ec
feminales are of a compound nature ; the tellieles
have a good deal the appearance of thofe of the mam~
molia.
They are of an oval form, and are fixed to the infide
of the back, their convex furface is covered with feve¬
ral tubes of a bright golden colour. After thefe yellow
tubes have been removed, the tefticles are eafily unfold¬
ed ; like all the other fecretory organs of infects, they
feem to be nothing but a colleflion of convoluted vef-
fels. The veficulce fetninales, which are attached to the
tefticles, are formed into clufters. In the feafon of co¬
pulation, they increafe in bulk fo much as nearly to
occupy three-fourths of the abdomen ; they are full of
a limpid fluid, which is the femen.
The vafa deferentia, which in moft infers are very
fhort, in the blatta mucronata are of a confiderable
length, and form feveral convolutions before they ar¬
rive at the penis.
rY\\('penis, in infers, is either fingle or double. Thofe
which have a fingle penis, have it placed at the pofte-
rior extremity of the abdomen ; in the libeliuta, how¬
ever, it is placed at the anterior part: it is membrana¬
ceous externally ; internally it is compofed of a fubftance
analogous to the coipus cavernofum of other animals ;
its form is either cylindrical or conical; it is furniflied
with two feales, one on each fide, which form a fort of
wedge ; this wedge being introduced into the vagina of
the female, and the feales being feparated by means of
particular mufeles, which are fituated at their bafe, open
the vagina, and make way for the introdu&ion of the
penis.