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E H U 
E R U 
moil white butterfly. This is of a yellowish- 
white colour, spotted with black, and infests 
the leavesof cabbages, cauliflowers, and the In- 
dian cress, of which it eats of all the tender 
parts, leaving only the libres ent'ue ; so that 
whole plantations are often seen destroyed 
by them in autumn, especially such as are 
near large buildings, or are crowded with 
trees. There is no remedy against this evil 
but the pulling the creatures off before they 
are spread from their nests, and watching the 
butterflies, which are daily, in the hot wea- 
ther, depositing their eggs on these plants. 
These, however, feed principally on the out- 
side of the leaves of the plants, and are 
therefore the easier taken off; but the other 
kind lies near the centre, and therefore is 
with much more difficulty discovered. This 
is much larger ; and the skin is very tough, 
and ot a brown colour. It is called by the 
gardeners a grub, and is extremely perni- 
cious. The eggs which produce it are usu- 
ally deposited in the very heart or centre of 
the plant, particularly in cabbages ; and the 
creature, when formed, and grown to some 
size, eats it way through all the blades, and 
leaves its dung in great quantities behind it, 
which spoils the cabbage. This insect also 
burrows under the surface of the ground, and 
makes sad havoc among young plants, by 
eating off their tender shanks, and drawing 
them into its holes. This mischief is chiefly 
done in the night; but wherever a plant is 
seen thus destroyed, if the earth is stirred 
with a finger an inch deep, the creature will 
be certainly found, and this is the only way 
of destroying them. 
When these animals attack fruit-trees, the 
best preservative is to boil together a quan- 
tity of rue, wormwood, and the common to- 
bacco, of each equal parts, in common water, 
to make the liquor very strong, and sprinkle 
it on the leaves and young branches every 
night and morning, during the time when the 
iruit is ripening. 
Eruca; aquaticct, zuater caterpillars. It 
may seem incredible, that there is any such 
thing as a caterpillar wjiose habitation is under 
water ; but experience and observation prove, 
that there are such, and that they feed on the 
water-plants as regularly as the common 
kinds do on those at land. These are not 
named at random like many of the aquatic 
animals of the larger kinds, as the sea-wolf, 
the sea-horse, &c. which might as well be 
called any thing else as wolves and horses ; 
but they are properly what they are called, 
and do not respire in the manner of the fish- 
tribe, but by their stigmata as other cater- 
pillars. M. Reaumur, in his observations, 
met with two species of these ; the one upon 
the pond-weed, the other upon the lenticula 
or duck-meat. These are both very indus- 
trious animals ; but the first being much the 
largest, its operations are more easily distin- 
guished; This, though truly an aquatic ani- 
mal, swims but badly, and does not at all 
love to wet itself. The parent butterfly lays 
her egg on the leaf of a certain plant; and as 
soon as the young caterpillar is hatched, it 
gnaws out a piece of the leaf, of a roundish 
shape. This it carries to another part of the 
same leaf, and iays.it in such a maimer, that 
there may be a hollow between, in which it 
may lodge, it then fastens down this piece 
to the larger leaf with silk of its own spin- 
ning, only leaving certain holes at which it 
can put out its head, and get to gnaw any of 
the leaves that are near, it easily gets out, 
though the aperture is naturally small, since 
a little force from its body bends up the upper 
leaf and down the lower, both being flexible ; 
and when the creature is out, it has a sort of 
down that defends it from being wetted, and 
the natural elasticity of the leaves and of the 
silk joins the aperture up again, so that no 
water can get in. The leaves of this kind of 
plant are also naturally very slippery, and 
not easily wetted by water. It soon hap- 
pens that this habitation becomes too small 
forthe animal, in which case it makes just 
such another ; and after that, at times, se- 
veral others, each being only made fit for it 
at the size it is then of. The changes of this 
creature into the chrysalis and butterfly 
states are in the common method. The but- 
terfly gets out of a chrysalis which was placed 
on the surface of the water; the lightness of 
the animal easily sustains it on the water till 
its wings are dried, and then it leaves that ele- 
ment, never to return to it again. 
Erucje sylvestres, wood-caterpillars; the 
name of a sort of caterpillars which do 
not live, after the manner of others, on 
leaves of trees or plants, or open to our 
observation ; but under the bark, in the trunk 
and branches, and in the roots of trees, and 
sometimes in the body of fruits. These are 
easily distinguished from those worms and 
maggots which are found in roots and fruits, 
and owe their origin to flies of another kind ; 
but are liable to be confounded with a sort of 
animals, called by M. Reaumur, false or bas- 
tard caterpillars, which bear a great resem- 
blance in their figure to real caterpillars, but 
which have more legs than any of the true 
ones have, and are finally transformed into 
four-winged flics, which are not true butter- 
flies. 
The butterflies which are the parents of 
those caterpillars that lie immured in trees or 
fruits, lay their eggs on the surface ; and the 
young caterpillars, when hatched, eat their 
way in. What appears something surprising, 
however, in this is, that there usually is only 
one caterpillar in a fruit which is large enough 
to afford food to a great number; and if there 
are sometimes found two creatures within, 
one is usually a caterpillar, the other a worm 
of some oilier kind. 1 lie whole occasion of 
this is, that the operation of penetrating into 
the fruit is so difficult to the young animal, 
that it seldom succeeds in it; and though the 
butterfly deposits many eggs on each fruit, 
and these all hatch, yet it" is only here ami 
there one on a fruit that can find its way 
into it. 
These creatures, when once lodged in 
their prison, have nothing to do but to eat 
up the substances which inclose them, leav- 
ing the outer hard shell unhurt, which still 
serves as a case for them. This is a very fre- 
quent case in grains of corn, where the fari- 
naceous substance serves as aliment, and the 
hard outer skin becomes a firm hollow, case 
afterwards for the animal. The farinaceous 
substance in this case usually proves enough 
for the animal in its caterpillar state.; but if it 
does not, the creature has recourse to .a very 
singular expedient: it eats again its own ex- 
crement, and finds its now. stronger stomach 
able to separate nourishment from that very 
matter which had before passed off from its 
weaken stomach undigested. 
E R V 
Of these species of caterpillars, some go 
out of their prison in order to change intd 
their chrysalis, and thence into their butterfly 
state; but the greater number remain there, 
and pass through all their changes within. 
These caterpillars, like all the other kinds, 
have certain flesh-eating worms, whose pa- 
rents arc of the fly-kind, for their terrible] 
enemies and destroyers; and it is not unfre*] 
quent, on opening one of these spoiled fruits,! 
instead of the expected caterpillar, to find a] 
fly just ready to come out: this lias beca 
produced from the chrysalis of a worm, w hid'd 
had found its way into the fruit, and 1 ; 
eaten up the caterpillar, which was the ori- 
ginal possessor of the place. , 
ERUCTATIONS, in medicine, are (lie 1 
effect of flatulent foods, and the crudities 
thence arising. 
ERUPTION, in medicine, a sudden amt 
copious excretion of humours, as pusor blood ; 
it signifies also the same with exanthema, 
any breaking out ; as the pustules of the 
plague, small-pox, measles, &c. See Me- 
dicine. 
ERVUM, the lentil, a genus of the decan- 
dria order, in the diadelphia class of plants, 
and in the natural method ranking under the 
32nd order, papilionaceax The cal\ - is quin- 
quepartite, the length of the corolla. There 
are six species ; of which the most remarkable 
is the lens, or common lentil. It is cultivated 
in many parts of England, either as fodder 
for cattle, or for the seeds, which are fre- 
quently used in meagre soups. It is an an- 
nual plant, and rises with weak stalks about 
18 inches high, with winged leaves compos- 
ed of several pairs of narrow lobes, termi- 
nated by a clasperor tendril, which fastens 
to any neighbouring plant, and is thereby 
supported; the flowers come out three of 
four together, upon short footstalks from the 
side of the branches. They are small, of a 
pale purple colour, and are succeeded by] 
short Hat pods, containing two or three seeds- 
which are flat, round, and a little convex in 
the middle. The seeds of this plant are most 
commonly sown in the month of March'd 
where the land is dry; but in moist ground,, 
the best time is April. The usual quantity 
of seed allowed for an acre of land is from, 
one bushel and a half to two, bushels. If 
these are sown in drills in the same manner: 
as peas, they will succeed better than when 
sown broadcast: the drills should be a. 
toot and a half asunder, to allow room for the: 
Dutch hoe to clean the ground between! 
them; for if the weeds are permitted to gro\V 
among them, they will get above the lentils] 
and. starve them. 
There is another sort of lentil also cultivat- 
ed in this country, under the name of French- 
lentil. It is twice the size of the former, both 
in plant and seed ; and is much better worth 
cultivation than the other. It should be so\vi\ 
in March, after a single ploughing,, in the- 
ground that bore corn the year before. Ma- 
nure is not absolutely necessary, though it 
will undoubtedly increase the crop. Its 
grass is said to be very copious ; it may be 
mowed many times in the year, and affords a; 
healthy as well as an agreeable food to horses,, 
cows, and. sheep; the milk of cows fed with, 
it is said to be very copious and good. Long, 
and numerous pods ripen about the begin? 
ning of winter, which afford a new kind of 
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