NEUROPTERA. 191 
ish-brown. The mentonniére of the larve and nymph is sloped 
like a lozenge at the extremity, and terminated by two points. 
A. puella: Libellula puella, L,; Rees., ib., 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 mentonniére of the larve and 
nymphs forms a salient angle *. 
The other Subulicornes 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 wanting, and their abdomen is terminated by two or 
three sete. 
They form the genus 
EPHemMera, 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 sete. The antenne 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 tibiz very 
short, and almost confounded with the tarsi, which 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 Ephemere usually appear at sunset, in fine weather, in sum- 
mer and autumn, along the banks of rivers, lakes, &c., and some- 
times in such 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 Tipule, with the terminal fila- 
ments of their tail divergent. ‘There the sexes unite. The males are 
distinguished from the females by two articulated hooks at the extre- 
mity of their abdomen, with 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., XIII, p.15; Olivier, Encyc. Méthod., article Libellule; and 
especially the preceding Monographs, where the variety of species and of their 
sexual differences are carefully indicated—works that haye greatly facilitated the dis- 
entangling of their synonomy. 
