188 INSECTA. 
Flies, &c. that constitute their food, attract our attention and enable 
us to recognize them with facility. ‘Their head is large, rounded, or 
in the form of a broad triangle. They have two great lateral eyes *, 
and three simple ones situated on the vertex; two antennee, inserted 
into the forehead behind a vesicular prominence. composed of five or 
six joints, or at least of three, the last of which is compound and at- 
tenuated in the manner of a stylet; a semicircular arched labrum; 
two very strong, dentated, and squamous mandibles; maxillee termi- 
nated by a piece of the same consistence, that is dentated, s spinous, and 
ciliated on the inner side, with an unarticulated palpus laid on the 
back and representing the galea of the Orthoptera; a large, arched, 
trifoliate labium, of which the two lateral leaflets are palpi; a sort of 
epiglottis or vesicular and longitudinal tongue in the interior of their 
mouth; a thick and rounded thorax; a highly elongated abdomen, 
which is sometimes ensiform, and at others resembles a rod, termi- 
nated in the males by two lamellar appendages varying in form accord- 
ing to the species +, and, finally, short legs curved forwards. 
The under part of the second annulus of the abdomen contains the 
sexual organs of the males, and as those of the females are situated on 
the last ring, the coition of these Insects is effected in a different 
manner from that of others. ‘The male, first hovering over his fe- 
male, seizes her by the neck with the hooks that terminate the pos- 
terior extremity of his abdemen, and_ flits away with her. After a 
shorter or longer period, the latter, yielding to his desires, curves her 
abdomen downwards, and approximates its extremity to the genitals of 
the male, whose body is then bent into the form of a buckle. This 
junction frequently occurs in the air, and sometimes on the bodies 
where they alight. To lay her eggs, the female places herself on 
some aquatic plant that is raised but little above the water, into which 
she plunges the posterior extremity of her abdomen. 
The larvee and the chrysalides inhabit the water until the period 
of the ultimate metamorphosis, and, with the exception of wings, are 
tolerably similar to the perfect Insect. ‘Their head, however, on 
which the simple eyes are not perceptible, is remarkable for the sin- 
gular form of the piece which replaces the lower lip. Ht is a kind of 
mask, that covers the mandibles, maxilla, and almost the whole under 
part of the head. It is composed, 1. of°a principal triangular piece 
that is sometimes arched and sometimes flat, called by Reaumur the 
mentonniére (chin-cloth), articulated by a hinge, with a pedicle or sort 
of handle annexed to the head; 2. of two other pieces inserted at the 
superior and lateral angles of the former, movable at base, transversal, 
and either in the form of wide and dentated laminz, resembling 
shutters in their motion and the manner in which they close the mouth, 
* For their structure, see Cuv., Mém. de la Soc. d’Hist. Nat. de Par., 4to. p. 
41. 
+ MM. Van der Linden and Toussaint Charpentier have made a particular study 
of these appendages. ‘The latter has carefully figured all these varieties in his Hore 
Entomologice. The genus Petalura, Leach, Zool. Miscel., being essentially established 
on characters drawn from these appendages, appears to me to be inadmissible, and 
for the simple reason, that if this ground of division be once received, we shall have 
to establish almost as many genera as there are species. 
