838 E N T O M 
attain the imago, or fly ftate, which generally happens in 
about eleven days after the preceding change, the fuper- 
fluous humours are evaporated, and the pupa is contract¬ 
ed into the fifth ring of the fkin, and the four laft rings of 
the abdomen are filled with air, through the aperture in 
the refpiratory orifice of the tail. This may be feen by 
expoling the pupa for a fhort fpace to the rays of the fun, 
and then putting its tail in water, when It will breathe 
(tronger than it did before, and, by expreffing an air bub¬ 
ble out of its tail, and then fucking it in again, will ma- 
nifeftly perform the action of infpiration and expiration. 
If the exterior cafe be opened near this period, a wonder¬ 
ful variety of colours may be perceived through the fkin 
which invefts the pupa. The colours of many of the 
different parts are now changed ; fome parts from aqueous 
become membranaceous, fome flefhy, and others cruftace- 
ous. When the fly begins to appear, the exterior fkin is 
fecn to move about the third and fourth anterior ring; 
the infedft then ufes all its efforts to quit the interior and 
exterior ikin at one and the fame time. The exterior fkin 
is divided into four parts ; the infedt immediately after¬ 
wards breaks open its inner coat, and carting it off, efcapes 
from its prifon in the form of a beautiful fly. Having 
thus acquired its perfect rtate, the little animal which liv¬ 
ed before in water and mud, enters into a new feene of 
life, visits the fields and meadows, is tranfported through 
the air on its elegant wings, and fports in the wide expanfe 
with unrertrained freedom. For a view of this infect in 
the worm rtate, fee the Entomology Plate II. fig. i+. 
and for its imago or fly rtate, fee the engraving to the 
article Muse a. 
Another very curious aquatic infedt is the libellula , or 
dragon fly. This infedt partakes of almoft all colours, 
green, blue, crimfon, fcarlet, and white; fome unite a 
variety of the moll vivid tints, and exhibit in one animal 
more different rtuides than are to be found in the rainbow. 
But it is not to colour alone that their beauty is confined, 
it is heightened by the brilliancy of their eyes, and the 
delicate texture and wide expantion of their wings. The 
larva of the libellula is an inhabitant of the water, the fly 
itfelf is generally found hovering on its banks. The 
dragdn fly is exhibited in the Entomology Plate I. fig. 
io, i r ; and the larva and pupa in Plate 11 . fig. 15, 16. 
But for figures of the mod curious and elegant fpecies of 
the fly, fee the engraving to the article Lieellula. 
Thefe infedts are produced from an egg, which is de- 
poiited in the water by the parent; the egg finks to the 
bottom, and remains there till the worm finds ftrength to 
break the fliell. The larva is hexapode, and not fo long 
as the fly; on the trunk are four prominences or little 
bunches, which become more apparent as the larva in- 
creafes in fize, and changes its fkin. Thefe bunches con¬ 
tain the rudiments of the wings, which adorn the infect 
when in its perfedt rtate. The head of the larva is ex¬ 
ceedingly lingular, the whole fore part of it being cover¬ 
ed with a malk, having proper cavities to fuit the dif¬ 
ferent prominences of the face ; it is of a triangular form, 
growing Imaller towards the bottom ; at this part there 
is a knuckle that fits a cavity near the neck, on which it 
turns as on a pivot. The upper part of this mafk is di¬ 
vided into two pieces or iluitters, which the infedt can 
open or dofe at pleafure ; it can alfo let down the whole 
mafk whenever it pleafes. The edges of the rtuitters are 
jagged like a faw. It makes ufe of the mafk to feize and 
hold its prey. Thefe larva generally live and feed at the 
bottom of the water, fwimming only occalionally : their 
manner of moving in the water is curious, being by bid¬ 
den jerks ; but this motion is not occalioned by their legs, 
which at this time are kept clofe to the body ; it is by 
forcing out a ftream of water from the tail, that the body 
is carried forward ; this may be eafily perceived, by 
placing them in a flat veflel, in which there is only juft 
water enough to cover the bottom. Here the adtion of 
the water fquirted from the tail will be very vifible; it 
Will occafion a fmall current, and give a fenlible motion 
z 
O L O G Y. 
to any light bodies on the furface. This adtion can only 
be effedted at intervals, becaufe after each expulfion the 
infedt is obliged to inhale a frelli fupply of water. The 
larva will fometimes turn its tail above the furface of the 
water, and - ejedt a fmall ftream from it as from a little 
fountain, and that with confiderable force. 
The pupa differs but little from the larva ; the bunches 
containing the wings grow large, and begin to appear like 
four fliort thick wings. It is full as lively as the larva, 
feekingand enjoying its food in the fame manner. When 
arrived at its full growth, and ready to go through its laft 
change, it approaches the edge of the water, and fixes it- 
felf firmly to a piece of wood or other fubftance by its 
claws. It remains for fome time immoveable; the fkin 
then opens down the back, and on the head ; through 
this opening is exhibited the real head and eyes, and at 
length the legs; it then creeps gradually forward, draw¬ 
ing firft its wings, and then the body, out of the (kin. The 
wings, which are moiftand folded, foonexpand themfelves 
to their real fize ; the body is alfo extended till it has 
gained its proper length, which extenfion is accompliftied 
by the propelling force of the circulating fluids. When 
the wings and limbs have acquired fufficient ftrength, it 
enters on a more noble ftate of life : in this new feene it 
enj.oys the living fragrance of the richeft meadows, revels 
in delight, and, having laid the foundation for its future 
progeny, finks into an eafy dilfolution. In its mature 
ftate the dragon fly is of a ferocious difpofition, hovering 
in the air like a bird of prey, in order to feed on and de- 
flroy every fpecies of fly ; its appetite is grofs and vora¬ 
cious, net confining itfelf to fmall flies only, but the large 
flelh-fly, moths, and butterflies, are equally fubjedt ed to 
its tyranny. See the article Libellula. 
The female of the cynips or gall infedt, which lias no 
wings, partes through no transformation; while the male, 
which has four wings, partes through the pupa ftate in 
order to become a fly. The principal habitude of the 
female is this, that after impregnation by the male, and 
with a view to the prefervation of a future progeny, it 
fixes itfelf to the branch or leaf of a tree, where it makes 
a pundture, which, from the gelatinous matter thrown 
out by the infect, added to the fap of the vegetable, in- 
creafes in fize, and becomes a true gall ; here the female 
depofits an egg, for which the gall firft ferves as a nidus, 
and afterwards as an habitation for the larva. See thia 
curious procefs deferibed, with figures of the fly, under 
the article Cynips, vol. v. p. 519. 
The aphides, or plant lice, to arrive at their refpedtive 
ftate, pals through that of the femicomplete pupa, and 
their wings do not appear till they have quitted their 
pupa ftate ; but, as in all the families of the pucerons 
there are many which never become winged, we rriuft not 
forget that thefe undergo no transformation, remaining 
always the fame, without changing their figure, though 
they increafe in (ize and change their Ikin. See the ar¬ 
ticle Aphis, vol. i. p. 789. 
An infedt that mu ft cart off its exuvia, or moult five 
times before it attains the pupa ftate, as is the cafe with 
many of the caterpillars, may be confidered as compoled 
of five organized bodies inclofed within each other, and 
nouriflied by common vifeera placed in the center: what 
the bud of the tree is to the invifible buds it contains, 
fuch is the exterior part of the caterpillar to the interior 
bodies it conceals in its bofom. Four of thefe bodies 
have the fame eflential ftrudture, namely, that which is 
peculiar to the infedt in its larva or caterpillar ftate : the 
fifth body is that of the pupa. The refpedtive ftate of 
thefe bodies is in proportion to their diftance from the 
center of the animal ; tliofe that are fartheft off have 
mod confidence, or unfold themfelves fooneft. When 
the exterior body has attained its full growth, that inte¬ 
rior one which is next in order is conliderably unfolded; 
it is then lodged in too narrow a compafs, therefore it 
llretches on all fides the (heath which covers it; the vef- 
fels which nourifh the external covering, are broken by 
