APHIS. 
three weeks, and then cast off their last co- 
vering, the whole insect being, after this, 
of a bright yellow colour, the wings only 
excepted; but after this change they be- 
come of a deeper yellow, and in a very few 
hours, of a dark brown, if we except the 
body," which is something lighter coloured, 
and has a reddish cast. The males no 
sooner come to maturity than they copu- 
late with the females, who, in a day or two 
after their intercourse with the males, lay 
their eggs, generally near the buds. Where 
there are a number crowded together, they, 
of course, interfere with each other, in 
which case they will frequently deposit 
their eggs on other parts of the branches. — 
It is highly probable that the aphides de- 
rive considerable advantages by living in 
society ; the reiterated punctures of a great 
number of them may attract a larger quan- 
tity of nutricious juices to that part of the 
tree or plant where they have taken up 
their abode. The observations of Mr. Cur- 
tis on the aphides are chiefly intended to 
shew that they are the principal cause of 
blights in plants, and the sole cause of the 
honey-dew. He therefore calls them the 
aphis, or blighter ; and after observing, 
that, in point of numbers, the individuals of 
the several species composing it surpass 
those of any other genus in the country, 
speaks thus, in general terms, of the 
whole tribe. These insects live entirely on 
vegetables. The loftiest tree is no less lia- 
ble to their attacks than the most humble 
plant. They prefer the young shoots on 
account of their tenderness, and on this 
principle, often insinuate themselves into 
the very heart of the plant, and do irrepa- 
rable mischief before they are discovered. 
But, for the most part, they beset the foli- 
age, and are always found on the underside 
of the leaf, which they prefer, not only on 
account of its being the most tender, but as 
it affords them protection from the wea- 
ther, and various injuries to which they 
would otherwise be exposed. Sometimes 
the root is the object of their choice, 
which, from the nature of these insects 
one would not, a priori, expect; yet I 
have seen the roots of lettuces thickly be- 
set with them, and the whole crop rendered 
sickly and of little value ; but such in- 
stances are rare. They seldom attach 
themselves to the bark of trees, like the 
apliis salicis, ' which being one of our largest 
species, and hence possessing superior 
strength, is enabled to penetrate a sub- 
stance harder than the leaves themselves. 
In the quality of the excrement voided by 
these insects, there is something wonder- 
fully extraordinary. Were a person acci- 
dentally to take up a book, in which it is 
gravely asserted, that in some countries 
there were certain animals which voided li- 
quid sugar, he would lay it down, regarding 
it as a fabulous tale, calculated to impose 
on the credulity of the ignorant ; and yet 
such is literally the truth. Mr. Curtis col- 
lected some on a piece of writing-paper, 
from a brood of the aphis salicis, and found 
it to be sweet as sugar ; and observes, that 
were it not for the wasps, ants, flies, and 
other insects that devour it as quickly as it 
is produced, it might, no doubt, be collect- 
ed in considerable quantities, and by the 
processes used with other saccharine juices, 
might be converted into the choicest sugar 
or sugar-candy. The sweetness of this ex- 
crementitious substance, the glossy appear- 
ance it gave the leaves it fell upon, and the 
swarms of insects this matter attracts, led 
him to imagine the honey-dew of plants 
was no other than this secretion, which fur- 
ther observation has since fully confirmed ; 
and not, as its name implies, a sweet sub- 
stance falling from the atmosphere. On 
this opinion it is further remarked, that it 
neither falls from the atmosphere, nor issues 
from the plant itself, as is easily demon- 
strated. If it fell from the atmosphere, it 
would cover every thing it fell upon indis- 
criminately, whereas we never find it but 
on certain living plants and trees. We find 
it also on plants in stoves and green-houses 
covered with glass. If it exuded from the 
plant, it would appear on all the leaves ge- 
nerally and uniformly ; whereas its appear- 
ance is extremely irregular, not alike on 
any two leaves of the same tree or plant, 
some having none of it, and others being 
covered with it but partially. It is pro- 
bable that there never exists any honey- 
dew but where there are aphides ; though 
such often pass unnoticed, being hidden on 
the underside of the leaf : and wherever ho- 
ney-dew is observable upon a leaf, aphides 
will be found on the underside of the leaf 
or leaves immediately above it, and under no 
other circumstance whatever. If by acci- 
dent any thing should intervene between 
the aphides and the leaf next beneath 
them, there will be no honey-dew on that 
leaf : and thus he conceives it is inconfro- 
vertibly proved that aphides are the true 
and only source of honey- dew. Of the 
British species of aphides, one of the larg- 
est and most remarkable is the aphis salicis, 
