NEUROPTERA. 189 
or in the form of hooks or little claws. To this part of the mask 
where the mentonnicre is articulated with its pedicle, or the knee, 
and which appears to terminate it inferiorly when the mask is flexed 
upon itself, Reaumur applies the name of mentum. The Insect un- 
folds or extends it with great promptitude, and seizes its prey with 
the pincers of its superior portion. The posterior extremity of the 
abdomen sometimes presents five foliaceous and unequal appendages, 
which the animal can separate and approximate, in which case they 
form a sort of pyramidal tail; sometimes we observe the three elon- 
gated and pilose lamine ora sort of fins. We see these Insects unfold 
them every moment, open their rectum, fill it with water, then close 
it, and shortly afterwards ejaculate that water mixed with large bub- 
bles of air, a game which appears to facilitate their motions. The in- 
terior of the rectum * presents to the naked eye twelve longitudinal 
ranges of little black spots, approximated by pairs, resembling the pin- 
nated leaves of botanists. By the aid of the microscope we discern 
that each of these spots is composed of little conical tubes, organized 
like tracheze, and from which originate small branches that proceed to 
six large trunks of the principal trachee, that traverse the whole length 
of the body. 
Having attained the period of their ultimate metamorphosis, the 
nymphs issue from the water, climb along the stems of plants, fix 
there, and divest themselves of their skin. 
M. Poe, who has paid particular attention to the Insects of the 
island of Cuba, informs me that at a certain season of the year the 
northern winds sweep an innumerable host of a species of this genus 
—specimens of which he had the kindness to send me—into Havana 
or its environs. 
Fabricius, anticipated in this point by Reaumur, divides the Libel- 
lulz into three genera. 
LipeLuuta, Fab., 
Or Libellula proper, where the wings are extended horizontally 
when at rest. The head is almost globular, with very large, conti- 
guous or closely approximated eyes, and a vesicular elevation on the 
vertex, with an ocellus on each side; the other or anterior ocellus 
is much larger. The middle division of the labium is much smaller 
than the lateral ones ¢, which unite beneath by a longitudinal suture, 
and close the mouth exactly. The abdomen is ensiform and flattened. 
The larve and the nymphs have five appendages at the posterior 
extremity of the body, forming a pointed tail; their body is short, 
the mentonniére convex, in the form of a helmet, with the two pincers 
resembling shutters. 
L. depressa, L.; Rees., Insect. Aquat.,VI, vii, 3. Brown, some- 
what yellowish; base of the wings blackish; two yellow lines 
* Cuy. Mém de la Soc. d’Hist. Nat., 4to., p. 48. 
+ These lateral divisions or palpi present a remarkable difference in the three sub- 
genera, 
