quantities, as to lay wafte great part of Europe, producing almoft
unequalled calamities, fwarming in fuch multitudes as to cloud
the air, deftroying all the vegetables; in Sweden the cattle-
perifhed with hunger* and the men were forced to, abandon their
country, and fly to the neighbouring regions* The far greater
part feed only, however, on one fpeeies o f plant, or at molt on
thefe-which are fimilar to it; and the fame fpecies.may always be
found on the fame plant.
Mr. de Reaumur fays, that the caterpillar, which mfefts and-
feeds upon the cabbage, deftroys in twenty-four hours more than
twice it’s weight. If larger animals required a proportionable
quantity, the ear-th would not be able to nourilh it!s. inhabitants.
A great number o f infects rejeft-vegetable, and-live on animal:
food; fome feeking that which is. beginning to, putrefy, while-
ethers delight in that which, is entirely putrid; others, again ar.e-
nourilhed by the moft filthy puddles, and difgufting. excrements;
fome attack and feed on man himfelf, while others are nourifhed
by his viftuals, his cloaths, his furniture: fome prey upon-,
infefts o f another fpeeies, othercatt ack their own, and harrafs
each other with perpetual carnage..
Every animal'has it’s appropriate lice, which feed'on and infeft
it. M. Rhedi has given an accurate account o f a great number,
o f thefe little noxious creatures; accompanied with figures.; but,
as if it were not fufficient that thefe creatures Ihould dwell and
live on the external part of the body, , and. fuck the blood of the
animal
* Seleft Diflertations from the AmcaniUtes Academic®, vol. I, P- 398-
animal that they infeft, we find another fpeeies o f infefts feeking
their food in the more vital parts, and feeding on the flefli of- the
animal, while full of life and health. M. de Reaumur has given
an hiftory of a fly (oeftrus bovis) which lives upon the backs, and
feeds on the flefli of young oxen and. cows, where it produces a
kind o f tumor. The fly lodges it’s eggs in the flefh, by making a
number of little wounds, in each o f which it depofits eggs, fo that
every wound becomes a nefl, the eggs of which are hatched by
the heat o f the animal. Here the larva finds abundant food at
the fame time that it is protefted from the changes o f the weather
; and here they flay till they are fit for transformation. The
parts they inhabit are often ea-fy to be 'difc-overed by a kind of
lump, or tumor, which they form by their ravages,; this tumor
fuppurates, and is filled with matter; on this difgufling fubflance
the larva feeds, and his head is always found plunged in it.
When the time of their metamorphofis is ready, the larva' falls
upon the ground, and feeks a convenient place for the operations
o f the enfuing change: .
There is a fpeeies (oeftrus haemorrhoidalis) which depofit their
eggs in the reftum of horfes; it being in the inteftines o f thefe
only that they can be nourifhed. M. Vallifinieri has. given an
account of the introduftion o f thefe eggs into the horfe, as ob-
ferved by a friend of his who was. looking at fome that were
feeding quietly in a meadow : on a Ridden they began to leap and
jump, roll themfelves on the ground, then run, beat about their
rails, and were otherwife violently agitated; perfuaded that thefe
extraordinary motions were produced by a fly that was buzzing
about-them, he obferved them narrowly. The fly not being able
to fuc-ceed in it’s attacks oh thefe, quitted them, and flew towards
L 1 2 a mare,