There are usually found in the month of June, especially near water,
certain insects that are called Ephemera, and which long ago acquired
true celebrity, and furnished material for comparison to poets and
philosophers. Indeed, in the adult state they live but one day, a fact
that has given them their name. They appear for a few hours, fluttering
about in the rays of a sun whose setting they are not to see, as they
live during the space of a single twilight only. These insects have
very short antennæ, an imperfect mouth incapable of taking food, and
delicate, gauze like wings, the posterior ones of which are always
small, or even rudimentary or wanting. Their legs are very delicate--the
anterior ones very long--and their abdomen terminates in two or three
long articulated filaments. One character, which is unique among
insects, is peculiar to Ephemerids; the adults issuing from the pupal
envelope undergo still another moult in divesting themselves of a thin
pellicle that covers the body, wings, and other appendages. This is what
is called the _subimago_, and precedes the imago or perfect state of the
insect. The short life of adult May-flies is, with most of them, passed
in a continual state of agitation. They are seen rising vertically in
a straight line, their long fore-legs stretched out like antennæ, and
serving to balance the posterior part of the body and the filaments
of the abdomen during flight. On reaching a certain height they allow
themselves to descend, stretching out while doing so their long wings
and tail, which then serve as a parachute. Then a rapid working of these
organs suddenly changes the direction of the motion, and they begin to
ascend again. Coupling takes place during these aerial dances. Soon
afterward the females approach the surface of the water and lay therein
their eggs, spreading them out the while with the caudal filaments, or
else depositing them all together in one mass that falls to the bottom.
These insects seek the light, and are attracted by an artificial one,
describing concentric circles around it and finally falling into it and
being burnt up. Their bodies on falling into the water constitute a food
which is eagerly sought by fishes, and which is made use of by fishermen
as a bait.
But the above is not the only state of Ephemerids, for their entire
existence really lasts a year. Linnæus has thus summed up the total life
of these little creatures: "The larvæ swim in water; and, in becoming
winged insects, have only the shortest kind of joy, for they often
celebrate in a single day their wedding, parturition, and funeral
obsequies." The eggs, in fact, give birth to more or less elongated
larvæ, which are always provided with three filaments at the end of
the abdomen, and which breathe the oxygen dissolved in the water by
tracheo-branchiæ along the sides of the body. They are carnivorous, and
live on small animal prey. The most recent authors who have studied
them are Mr. Eaton, in England, and Mr. Vayssiere, of the Faculte des
Sciences, at Marseilles.
_A propos_ of the larvæ of Ephemera or May-flies, we must speak of one
of the entomological rarities of France, the nature and zoological place
of which it has taken more than a century to demonstrate. Geoffroy, the
old historian of the insects of the vicinity of Paris, was the first to
find in the waters of the Seine a small animal resembling one of the
Daphnids. This animal has six short and slender thoracic legs, which
terminate in a hook and are borne on the under side of the cephalic
shield. This latter is provided above with two slender six-jointed
antennæ, two very large faceted eyes at the side, and three ocelli
forming a triangle. The large thoraceo-abdominal shield is hollowed out
behind into two movable valves which cover the first five segments of
the abdomen (Fig. 1). The last four segments, of decreasing breadth,
are retractile beneath the carapax, as is also the broad plume that
terminates them, and which is formed of three short, transparent, and
elegantly ciliated bristles. These are the locomotive organs of the
animal, whose total length, with the segments of the tail expanded, does
not exceed seven to eight millimeters. The animal is found in running
waters, at a depth of from half a meter to a meter and a half. It hides
under stones of all sizes, and, as soon as it is touched, its first care
is to fix itself by the breast to their rough surface, and then to swim
off to a more quiet place. It fastens itself so firmly to the stone that
it is necessary to pass a thin knife-blade under it in order to detach
it.
[Illustration: FIG. 1.--LARVA OF MAY FLY. (Magnified 12 times.)]
Geoffroy, because of the two large eyes, and without paying attention to
the ocelli, named this larva the "feather-tailed binocle." C. Dumeril,
in 1876, found it again in pools that formed after rains, and named the
creature (which is of a bluish color passing to red) the "pisciform
binocle." Since then, this larva has been found in the Seine at
Point-du-Jour, Bas-Meudon, and between Epone and Mantes. Latreille,
in 1832, decided it to be a crustacean, and named it _Prosopistoma
foliaceum_. In September, 1868, the animal was found at Toulouse by Dr.
E. Joly in the nearly dry Garonne. Finally, in 1880, Mr. Vayssiere met
with it in abundance in the Rhone, near Avignon.
The abnormal existence of a six-legged crustacean occupied the
attention of naturalists considerably. In 1869, Messrs. N. and E. Joly
demonstrated that the famous "feather-tailed binocle" was the larva of
an insect. They found in its mouth the buccal pieces of the Neuroptera,
and, under the carapax, five pairs of branchial tufts attached to the
segments that are invisible outwardly. Inside the animal were found
tracheæ, the digestic tube of an insect, and malpighian canals.
Finally, in June, 1880, Mr. Vayssière was enabled to establish the fact
definitely that the insect belonged among the Ephemerids. Two of the
larvae that he raised in water became, from yellowish, gradually brown.
Then they crawled up a stone partially out of water, the carapax
gradually split, and the adults readily issued therefrom--the head
first, then the legs, and finally the abdomen. At the same time, the
wings, which were in three folds in the direction of their length,
spread out in their definite form (Fig. 2). The insects finally flew
away to alight at a distance from the water. The wings of the insect,
which are of an iron gray, are covered with a down of fine hairs. The
posterior ones soon disappear.
[Illustration: FIG. 2.--MAY-FLY (adult magnified 14 times).]
Perhaps the subimago in this genus of Ephemerids, as in certain others,
is the permanent aerial state of the female.--_La Nature_.
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Connecticut is rapidly advancing in the cultivation of oysters. About
90,000 acres are now planted, and thirty steamers and many sailing
vessels are engaged in the trade.
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