576 
INSECTA. 
Agrioti, Fabr., has the wing's elevated perpendicularly in repose ; the head transverse, with the eyes apart ; the 
form of the lower lip is similar to that of ^shna, but its middle lobe is slit to the base. The forehead is not fur- 
nished with a vesicle; the ocelli are nearly equal in size, and arranged in a triangle on the vertex ; the abdomen 
is very slender and filiform, and occasionally very long. The body in the larva and pupa states is also long and 
slender, and the abdomen terminated by two oar-like appendages ; the mask is flat, with the superior extremity of 
the chin-piece elevated into a point in some, and forked in others. Lihellula virgo, Linn., is of a golden-green 
or bluish-green colour, with the wings blue, either entirely or partially, and sometimes pale brownish-yellow. 
[This and several other species of smaller size, belonging to the subgenera separated from Agrion by Leach, are 
of very common occurrence in this country.] 
The other Subulicorn Neuroptera have the mouth entirely membranous or very soft, and com- 
posed of parts very indistinct ; they have 5 -jointed tarsi; the lower wings are much smaller than the 
superior, or even wanting ; and the abdomen is terminated by two or three long threads. They form 
the genus 
Ephemera, Linn., — 
Thus named from the short duration of their life in the perfect state. The body is soft, long, slender, 
and terminated behind by two or three long articulated filaments. The antennm are very small, and 
composed of three joints, of w^hich the last is very long, in the form of a conical thread. The front of 
the head is advanced like a hood, often keeled and notched, and covers the mouth, of which we cannot 
trace the organs on account of their softness and smallness. These insects carry their wings almost 
always elevated perpendicularly, or but slightly deflexed, like the Agrions. The legs are veiy slender, 
with the tibiae very short and united to the tarsi, which have often only four joints, the first being 
nearly obsolete. The two ungues of the terminal joint are very compressed, and the fore-legs are much 
longer than the others. 
The Ephemer<s generally appear at sunset in the fine days of summer and autumn, along rivers, lakes, &c., and 
sometimes in such numbers that the ground, after their death, is covered with them, so that they are carted away 
as manure. The falling of one species, with white wings, resembles that of a fall of snow. 
These insects unite in swarms in the air, where they fly up and down, extending the threads of their tails. It is 
there also that the sexes unite, the males being distinguished by two hooks at the extremity of the body ; their 
fore-legs and anal threads are also longer, their eyes larger, and some males possess four eyes, two being much 
larger, and elevated on columns. The females deposit their eggs in a gelatinous mass, and, as the propagation of 
the species is the only object of the existence of the individual, they very soon perish, often on the day in which 
they undergo the final change, sometimes living only a few hours. Those' which .fall on the water are greedily 
seized by the fishes, and fishermen give them the name of Manna. But if we consider them in the larva state, 
we find their existence extending through two or 
three years. In this, and the pupa state, they reside 
in the water, concealed during the day under stones, 
or in horizontal burrows, which they form in the 
banks, from which it is supposed that these larvae 
derive their food. Although resembling the perfect 
insect in several respects, they differ materially in 
having longer antennae, wanting ocelli ; by possess- 
ing horn-like mandibles; the abdomen has, more- 
over, on each side, a row of plates, mostly in pairs, 
which are a kind of false branchiae, and which are 
employed not only in respiration, but also as paddles. 
The pupa differs from the larva by possessing scales 
inclosing the wings. At the moment when they un- 
dei’go this change they quit the water, and appear, 
after casting their skin, under a new form ; but, by 
Fig. 106. — Ephemera vulgata : larva, pupa, and imago. 
a singular exception, they have to undergo another moulting before they are fit for propagation. Their last exuviae 
are often found fixed to trees, and upon walls. 
De Geer formed these insects and the Plirygane<e into a distinct order, in consequence of the minuteness or 
absence of the parts of the mouth. In the TabUau Elementaire of Cuvier they also form a peculiar group, named 
Agnatha, but which formed part of the order Neuroptera. 
The number of the wings and of the anal filaments lead to the establishment of various divisions in the genus 
Ephemera ; some having four wings and two tails {E. Swammerdamiana) ; others four wings and three tails 
{Ephemera proper, E. vulgata, Linn.) ; some with two wnngs and three tails, and the eyes of the male doubled, one 
pair placed in foot stalks. [Others again have only two wings and two tails. These various groups have been 
formed into separate genera by Leach, and other subsequent authors, E. vulgata, the commonest species, and 
which is well known to fly-fishers under the name of the Grey Drake, being retained as the type of the restricted 
genus Ephemera.] 
