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 antennae, 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; maxillae termi- 

 nated by a piece of the same consistence, that is dentated, 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 f, 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 abdomen, 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 larvae 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. It is a kind of 

 mask, that covers the mandibles,'maxillae, 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 

 mentonniere (chin-cloth), artic\ilated 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 foimer, movable at base, transversal, 

 and either in the form of wide and dentated laminae, resembling 

 shutters in their motion and the manner in which they close the mouth, 



* For their structure, see Cuv., Mem. de la Soc. d'Hist. Nat. de Par., 4to. p. 

 41. 



f 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 Horcc 

 Entomologies. The genus Pefalura, Leach, Zool. Miscel., being essentially establislied 

 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. 



