APHIS. 
greater axis of the elliptical orbit of the 
planet, most remote from the focus wherein 
the sun is. The times of the aphelia of the 
primary planets may be known by their 
apparent diameters appearing least ; as also, 
by their moving slowest in a given time. 
They may likewise be found by calculation, 
the method of doing which is delivered in 
most astronomical writers. 
Sir Isaac Newton and Dr. Gregory have 
proved that the aphelia of the primary pla- 
nets are at rest. See Princip. prop. 1 4. 
lib. S. And in the scholium to the above 
proposition they say, that the planets near- 
est to the sun, viz. Mercury, Venus, the 
Earth, and Mars, from the actions of Jupi- 
ter and Saturn upon them, move a small 
matter in consequentia with regard to the 
fixed stars, and that in the sesquiplicate ra- 
tio of their respective distances from the 
sun. 
APHIS, in entomology, a genus of the 
Hemiptera order, which has engaged the 
attention of naturalists for various reasons : 
their generation is equivocal, and their in- 
stinctive economy differs ; in some respects, 
from that of most other animals. Linnams 
defines the generic character of the aphis 
thus ; beak inflected, sheath of five articu- 
lations, with a single bristle ; antennae se- 
taceous, and longer than the thorax ; either 
four erect wings, or none ; feet formed for 
walking; posterior part of the abdomen 
usually furnished with two little horns. 
Geoffroy says, the aphides have two beaks, 
one of which is seated in the breast, the 
other in the head ; this last extends to, and 
is laid upon the base of the pectoral one, 
and serves, as that writer imagines, to con- 
vey to the head a part of that nouxishment 
which the insect takes, or sucks in, by 
means of the pectoral beak. Gmelin emx- 
merates about 70 species, all of which, 
and doubtless many others, are found 
in different parts of Europe. They in- 
fest an endless variety of plants ; and it 
is believed each species is particularly at- 
tached to one kind of vegetable only ; 
hence each sort has been hitherto uniform- 
ly named after the individual species or ge- 
nus of plants on which it feeds ; or if that 
could not be ascertained, that on which it 
had been found ; for some species are ra- 
ther uncommon and little known, though 
others are infinitely too numerous. The 
aphides are sufficienly knowu by the indis- 
crimate term of plant-lice; they abound 
with a sweet and grateful moisture, and 
are therefore eagerly devoured by ants, 
the larva of coccinellae, and many other 
creatures, or they would become, very pro- 
bably, more destructive to the whole vegetar 
ble creation than any other race of insects 
known. If Bonnet was not the first na- 
turalist (as is generally acknowledged) who 
discovered the mysterious course of genera- 
tion in the aphides, or,, as he calls them, 
pucerons, his experiments, together with 
those of his countryman, Trembly, tended 
at least to confirm, in a most satisfactory 
manner, the almost incredible circum- 
stances i-especting it, that an aphis or pu- 
ceron, brought up in the most perfect soli- 
tude from the moment of its birth, in a 
few days will be found in the midst of a nix- 
merous family ; and that if the expei'iment 
be again repeated on one of the individuals 
of this family, a second generation will 
multiply like its parent ; and the like expe- 
riment may be many times repeated with 
the same effect. 
The history of aphides has also been 
very copiously treated upon by Dr. Rich- 
ardson, in a paper printed in the 41st vol. 
of the Philosophical Transactions ; and by 
the late ingenious Mr. Curtis, in the sixth 
volume of the Transactions of the Linnasan 
Society. The tenor of Dr. Richardson’s 
remarks is briefly this : the great variety 
of species which occur in the insects now 
under consideration may make an inquiry 
into their particular natures seem not a lit- 
tle perplexing, but by reducing them un- 
der their proper genus, the difficulty is con- 
siderably diminished. We may reasonably 
suppose all the insects, comprehended un- 
der any distinct genus, to partake of one 
general nature ; and by diligently examin- 
ing any particular species, may thence gain 
some insight into the nature of all the rest. 
With this view, Dr. Richardson chose out 
of the various sorts of aphides the largest 
of those found on the rose-tree; not only 
as its size makes it more conspicuous, but 
there are few of so long duration. This 
sort appears early in the spring, and conti- 
nues late in autumn, while several are li- 
mited to a much shorter term, in conformi- 
ty to the.' different trees and plants whence 
they draw their nourishment. If, at the 
beginning of February, the weather hap- 
pens to be so warm as to make the buds of 
the rose-tree swell and appear green, small 
aphides are frequently to be found on them, 
though not larger than the young ones in 
summer when first produced. It will be 
found, that those aphides which appear only 
in spring, proceed from small black oval’eggs. 
