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straight, or are folded up transversely ; in others they are doubled up, or folded longi- 
tudinally, like a fan ; sometimes they are horizontal, sometimes inclined like a roof ; in 
many they meet upon the hack, and in others they are wide apart.* The two-winged 
insects, of the dipterous order, have also, beneath their wings, two small moveable 
threads, terminated by a mass, and which, according to the ordinary opinion, replace 
the pair of v/ings which are deficient; they are called balancers t {halteres). Other 
two-winged, very extraordinary insects, have also two balancers, but situated at the 
anterior extremity of the thorax, and which we name, to distinguish them from the 
others, prebalancers {prehalteres) . Above the true balancers is a small membranous 
scale, formed of two pieces, united at one of the edges, and resembling the two shells 
of a bivalve mollusc : this is the alulet, or cueilleron [alula] . Some aquatic Beetles 
also exhibit it beneath the elytra, inserted at their base. 
Many insects, such as the Cockchafers, Cantharides, &c., have, instead of the two 
upper or anterior wings, two scale-like pieces, more or less thickened, and more or less 
solid and opaque, which open and shut, and beneath which the wings are transversely 
folded in repose. These scale-like pieces have received the name of elytra.% The in- 
sects which are furnished with these organs are called Coleoptera, or insects in a sheath. 
These pieces are never wanting §, but this is not always the case with respect to the 
wings themselves. In other kinds of insects, the extremity of these scales is entirely 
membranous, like the wings; and in this case these pieces are called hemelytra : [hence 
the name of the Linnaean order Hemiptera]. 
The scutellum, or escutcheon, is ordinarily a triangular piece, situated upon the back 
of the mesothorax, between the places of insertion of the elytra, or wings. It is some- 
times very large, and then covers the greater portion of the upper side of the abdomen. 
Various Hymenoptera exhibit behind it, upon the metathorax, a small space called the 
false escutcheon (post-scutellum ) . 
The legs are composed of a haunch of two joints [coxa and trochanter], a thigh 
[femur], a shank of a single joint [tibia], and a finger, commonly called the tarsus, 
which is divided into several phalanges, or joints, the number of which varies from 
three to five, depending chiefly upon the changes which the first and penultimate joints 
suffer in their relative proportions. Although the counting of these joints may some- 
times prove difficult [from their minuteness] , and the numerical series may not always 
be in relation with the natural system, it nevertheless forms a good character for the 
distinction of genera : the last joint is generally terminated by two hooks. The form 
of the tarsi is subject to some modifications, according with the habits of the insects. 
Those of the aquatic species are generally flattened, very much fringed, and resemble 
oars. II 
The abdomen, which forms the third and last part of the body, is confounded with 
* That is, when the insect is in inaction. The rapidity of the vibra- 
tions of the wings appears to us to be one of the chief causes of the 
humming noise which many make. The explanations which have been 
given of it are not satisfactory. [Bnrmeister, and some others, have 
considered, more recently, that it is by the action of the air passing 
rapidly through the raetathoracic spiracles, during flight, that this 
noise is produced]. 
{• These are appendages, in my opinion, of the tracheae of the first 
abdominal segment, and correspond to the space pierced with a small 
hole adjacent to the anterior edge of an orifice, with a membranous, 
internal diaphragm on each side of the same segment in the Locusts. 
(See my memoir on the articulated appendages of insects in the Mim. 
du Mus. d’Hist. Nat.) [On the supposition that the terminal part of 
the thorax of the Diptera is in fact thoracic, and not abdominal, as in- 
sisted upon by Latreille, these balancers will necessarily become 
metathoracic, and, as such, must be considered analogous to the 
posterior pair of wings. The large size of the true wings, and of the 
mesothorax, is in favour of this view of the subject, the alula, as it 
seems to me, being nothing but a portion of the fore-wing.] 
t See M. Odier’s memoir on the chemical composition of these 
organs, inserted in the Mhn. Society d’Hist. Nat. de Paris [translated 
in the Zoological Journal). 
§ [Latreille has evidently overlooked the female of the Glow-worm, 
that of Drilus flavescens, and of Pachypus excavatus, all of which have 
neither elytra nor wings, although belonging to the order Coleoptera.] 
I Mr. Kirby, in his monograph of the Bees of England, and in his 
excellent Introduction to Entomology, calls the tarsi of the fore-legs 
the hand, the first joint being the palm. 
