NEUROPTERA. 191 



ish-broAvn. The mentonniere of the larvae and nymph is sloped 

 like a lozenpfe at the extremity, and terminated by two points. 



A. puella : Libetlula puella, L,; Roes., lb., x, xi. Very va- 

 rious as to colour ; its abdomen is most commonly annulated with 

 black, and the wings are colourless. 

 The superior extremity of the mentonniere of the larvae and 

 nymphs forms a salient angle *. 



The other Subulicorncs have an entirely membranous or very soft 

 mouth, composed of parts that are rather indistinct. Their tarsi con- 

 sist of five joints ; their inferior wings are much smaller than the su- 

 perior, or even Avanting, and their abdomen is terminated by two or 

 three setie. 



They form the genus 



Ephemera, Lin., 

 So called from their short term of life, in their perfect state. Their 

 body is extremely soft, long, tapering, and terminated posteriorly by 

 two or three long and articulated setae. The antennae are very 

 small and composed of three joints, the last of which is very long, and 

 in the form of a conical thread. The anterior part of their head pro- 

 jects in the manner of a clypeus, frequently carinated and emargi- 

 nated, covers the mouth, the organs of which are so soft and exigu- 

 ous that they cannot be distinguished. The wings of those Insects are 

 always placed perpendicularly, or slightly inclined posteriorly, like 

 those of an Agrion. The legs are very slender, and the tibiae very 

 short, and almost confounded with the tarsi, Avhich frequently present 

 but four joints, the first having nearly disappeared ; the two hooks of 

 the last one are strongly compressed into the form of a little palette ; 

 the two anterior legs, much shorter than the others, are inserted al- 

 most under the head, and directed forwards. 



The Ephemerae usually appear at sunset, in fine weather, in sum- 

 mer and autumn, along the banks of rivers, lakes, &c., and some- 

 times in svich innumerable hosts that after their death the surface of 

 the ground is thickly covered with their bodies ; in certain districts 

 cart-loads of them are collected for manure. 



The descent of a particular species — the albipennis — remarkable 

 for the shortness of its wings, recals to our minds a heavy fall of 

 snow in winter. 



These Insects collect in flocks in the air, flitting about and balanc- 

 ing themselves in the manner of the Tipulae, with the terminal fila- 

 ments of their tail divergent. There the sexes unite. The males are 

 distinguished from the females liy two articulated hooks at the extre- 

 mity of their abdomen, Avith which they seize them. It also appears 

 that their anterior legs and caudal filaments are longer than those of 



the females, and that their eyes are larger ; some of them even have 



• 



* For the other species, see Fabricius, Entom. Syst. ; Lat., Hist. Gener. des 

 Crust, et des Insect., Xlil, p. 15; Olivier, Encyc. Method., article LibdMe ; and 

 especially the preceding Monographs, where the variety of species and of their 

 sexual dififerences are carefully indicated — works that have greatly facilitated the dis- 

 entangling of their synonomy. 



