NEUROPTERA. 189 



or in the form of liooks or little claws. To this part of the mask 

 where the mentonniere is articulated with its pedicle, or the knee, 

 and which appears to terminate it inferiorly when the m .sk is floxed 

 upon itself, Reaumur applies the name of mentum. The Insect un- 

 folds or extends it with great promjititude, 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 laminae or a sort of fins. We see these Insects unfold 

 thein 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 Jblack spots, approximated by pairs, resembling tlie 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 tracheae, and from which originate small branches that proceed to 

 six large trunks of the principal tracheae, 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- 

 lulse into three genera. 



LiBELLULA, Fab., 



Or Libellula proper, where the wings are extended liorizontally 

 when at rest. The head is almost globular, with very large, conti- 

 guous or closely approximated e}^es, 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 f , which unite beneath by a longitudinal suture, 

 and close the mouth exactly. The abdomen is cnsiform and flattenerl. 

 The larvae and the nymphs have five appendages at the posterior 

 extremity of the body, forming a pointed tail ; their body is short, 

 the mentonniere convex, in the form of a helmet, with the two pincers 

 resembling shutters. 



L. dfpressa,\j.; Roes., Insect. Aquat.,VI, vii, 3. Brown, some- 

 what yellowish; base of the wings blackish; two yellow lines 



* Cuv. M^m de la Soc. d'Hist. Nat., 4to., p. 48. 



t These lateral divisijns or palpi present a remarkable difference in the three sub- 

 genera. 



