576 



INSECTA. 



Agrion, Fabr., lias tlie wingfs elevated perpendicularly in repope ; the head transverse, with the eyes apait ; ^iie 

 form of the lower lip is similar to that of vEshna, but its middle lobe is slit to the base. The forelieadis not ft-r- 

 nishcdwith a vesicle; the ocelli are nearly equal in size, and aiTanj;;ed in a trian^de on the vertex ; the abdomen 

 is very slender and fiJiform, 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 appendai^es ; tlie mask is flat, with the superior extremity of 

 the chin-piece elevattd into a point in some, and forked in others. LibeUula virgo, Linn., is of a golden-green 

 or bluish-green colour, wUh the wings blue, either entirely or partially, and sometimes pale brownish-yellow. 

 [Tins and several other species of smaller size, belonging- to the subgenera separated fruni Agi^ion by Leucli, are 

 of very common occurrence in this couiitiy.] 



The other Subulicorn Neuroptera have the mouth entirely membranous or very Mjft, and com- 

 posed of \y.\xX^ very indistinct ; they have .^-joirjtcit tursi ; the lower win^^s arc rauch 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 I'Crfect state. The body is soft, long, slender, 

 and terminated behind by two or three long articulated filaments. The antennae are very small, and 

 composed of three joints, of which 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 orifan^ on ace iiii;i of their softucis and sinalhiess. The^c insects carry their wings almost 

 always elevated })erpciidieularly, or but slightly deOexed, like the Agrions. The legs arc veiy slender, 

 with the tiliiic \ery short and united to the tarsi, "which ha^e often only four joitits, the first being 

 nearly olisolete. The two ungues of the terminal joint arc very compressed, and the fore-legs are much 

 longer tliaii the others. 



Th.eEpJiL'iiicrt.e generally appear at sunset in the fine days of summer and autumn, along rivers, lakes, Szc, and 

 sometimes in such numbers that the ground, after their death, is covered with tliem, 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 

 ill the water, concealed during the day under stone'-, 

 or in horizontal burrows, which they form in the 

 banks, from which it is supposed that thtse larvae 

 derive their food. Although resembling the perfect 

 insect in several respects, they differ materially in 

 having longer antenucX, wanting ocelli ; by possess- 

 ing horn-like mandibles; the abdomen has, more- 

 over, on each side, a row of plates, mostly in pairs, 

 which arc a kind of false branchiie, and which are 

 employed not only in respiration, but also as paddles. 

 The pupa diflers from the larva by possessing scales 

 inclosing the wings. At the moment when they un- 

 dergo this change they quit the water, and appear, 

 after casting their skin, under a now form ; but, by 

 a singular exrcption, tliey have to undergo anotlicr moulting before they .'ux' fd fur pi-u]iagation. Tlit-ir last exuviae 

 are often found fixed to trees, and upon walls. 



I)e Geer formed these insects and the P/irpganea into a distinct order, in consequence of the minuteness or 

 absence of the parts of the mouth, In the Tableau Elcmcntalrc of Cuvier they also form a peculiar group, named 

 Jll>uilli<i, but wliich formed part of the order Neuroptera. 



Tlie nuuiber of tlie wings and of the anal filaments lead to the establishment of \'arions divisions in the genus 

 Ephemera; some having four wings and two tails {E. Swarnmerdamiana) ; others four wings and three tails 

 (Ejihcmcra proper, E.vulgata, Linn.); some with two wings 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 autliors, E. vuhjafa, the commonest species, and 

 v:).'ich is well known to fly-fishers under the name of the Grey Drake, being retained as the type of the restricted 

 gnius iLphemcra.] 



Fib'. KIG._Ef.hem 





