in some
years than others, and are then seen in swarms for many evenings near
the lakes or rivers whence they arise; and, I suppose, emigrate to
upland situations, where fewer of them are produced. About thirty
years ago such a swarm was observed by Mr. Whitehurst for a day or two
about the lofty tower of Derby church, as to give a suspicion of the
fabric being on fire.

Many other kinds of flies have their origin in the water, as perhaps
the whole class of neuroptera. Thus the libellula, dragon fly: the
larva of which hurries amid the water, and is the cruel crocodile of
aquatic insects. After they become flies, they prey principally on the
class of insects termed lepidoptera, and diptera of Linneus. The
ephemera is another of this order, which rises from the lakes in such
quantities in some countries, that the rustics have carried cart-loads
of them to manure their corn lands; the larva swims in the water: in
its fly-state the pleasures of life are of short duration, as its
marriage, production of its progeny, and funeral, are often
celebrated in one day. The phryganea is another fly of this order; the
larva lies concealed under the water in moveable cylindrical tubes of
their own making. In the fly-state they institute evening dances in
the air in swarms, and are fished for by the swallows.

Many other flies, who do not leave their eggs in water, contrive to
lay them in moist places, as the oestros bovis; the larvae of which
exist in the bodies of cattle, where they are nourished during the
winter, and are occasionally extracted by a bird of the crow-kind
called buphaga. These larvae are also found in the stomachs of horses,
whom they sometimes destroy; another species of them adhere to the
anus of horses, and creep into the lowest bowel, and are called botts;
and another species enters the frontal sinus of sheep, occasioning a
vertigo called the turn. The musca pendula lives in stagnant water;
the larva is suspended by a thread-form respiratory tube; of the musca
chamaeleon, the larva lives in fountains, and the fly occasionally
walks upon the water. The musca vomitoria is produced in carcases;
three of these flies consume the dead body of a horse as soon as a
lion. Lin. Syst. Nat.

ADDITIONAL NOTE. V.

AMPHIBIOUS ANIMALS.

So still the Diodons, amphibious tribe,
With twofold lungs the sea and air imbibe.
CANT. I. l. 331.

D. D. Garden dissected the amphib