178 Micro sco pic At E ssays.
men ; through thefe the infeft is fuppofed to breathe : this Angular
circumftance in their refpiration forms another peculiar
charafter of infefts.
T he limbs, or the organs ufed by the infect for moving its
body, and for defending itfelf, are the tail, the fling, the. feet, the
wings, the halteres or poifeirs.
T he t a i l terminates the abdomen, and is conftrufted in a
wonderful manner for anfwering the purpofes for which it is
formed, namely, to direft the motion o f the infeft, to ferve as
an inftrument o f defence, or for depofiting the eggs ; the figure
and fize thereof varying in each genus and it’s families. In feme
it is fimple, Jimplex, and yet capable of being extended or drawn
back at pleafure. In others, elongala, elongated. Setaceous,
Ihapedlike a brittle; trifeta, with three.appendages like briftles;
in fome it is forked, fwrcata; and in others it is furnilhed with a
pair o f forceps, forcip a ta ; in the blatta and others it is foliofa,
or like a leaf. In the fcorpion and panorpa it is telifera, furnilhed
with a fling. Further particulars maybe obtained from
the Philofbphia Entomologica o f Fabricius.
A culeus, or fling, an inftrument with which infefts wound
and inftil a poifon; the fling generally proceeds from the under
part of the laft ring of the belly : in fome it is lharp and pointed, -
in others formed like a faw. It is ufed by many infefts both as
an offenfive and defenfive weapon ; by others it is only ufed to
pierce the fubftances where they mean to depofit their eggs.
Microscopical E ssays. i 79
P edes, the fe e t . Thefe are admirably adapted for
their intended fervice, to give the moft convenient and proper
motion, and from the variety in their conftmftion, their various
articulations, &c. furnilh the microfcopic obferver with a great
many curious and interefting objefts : the moft general number
is fix ; fome have eight, as the fpider; the crab has ten; the
onifcus fourteen; the julus has from feventy to one hundred and
twenty on each fide. The legs o f thofe infefts that have not
more than ten, are affixed to the trunk ; while thofe that exceed
that number have part fixed to the trunk, the reft to the
abdomen.
The legs o f infefts are generally divided into four parts. The
firft, which is ufually the largeft, is called the fem u r ; the
fecond, or tibia, is joined to the former, and is commonly o f the
fame fize throughout, and longer than the femur; this is followed
by the third part, which is diftinguiffied by the name o f
tarfus, or fo o t; it is eompofed o f feveral joints, the one articulated
to the other, the number o f the rings varying in different
infefts : the tarfus is terminated by the unguis, or claw.
The writers on natural hiftory, in order to render their
defcriptions clear and accurate, have given feveral names to the
legs o f infefts, from the nature of the motions produced by
them.
Thus curforii, from that of running; thefe are the moft
numerous.
The fa lta torii, thofe that are ufed for leaping.
Y '