An aphis, or puceron, brought up in the molt perfeft folitude
from the very moment o f it’s birth, in a few days will be found in
the midft o f a numerous family ; repeat the experiment on one of
the individuals o f this family, and you will find this fecond generation
will multiply like it’s parent, and. this you may purfue
through many generations.
Mr. Bonnet had repeated experiments o f this kind, as far as:
the fixth generation, which all uniformly prefented the obferves
with fruitful virgins, when he was engaged in a feries o f new and
tedious experiments, from a fufpicion imparted by Mr,. Trembley
in a letter to him, who thus expreffes himfelf: “ I have formed;
“ thedefign o f rearing feveral generations of folitary pucerons, in,
" order to fee i f they would all equally bring forth young. In
“ cafes fo remote from ufual circumftances, it is allowed,to try all
V forts o f means ; and I argued with myfelf, who knows but that.
“ one copulation might ferve for feveral generations ?” This.
“ w h o k n o w s " perfuaded Mr. Bonnet that he had not
fufficiently purfued his inveftigations. He therefore now reared
o the tenth generation:his folitary aphides, having the- patience
to keep an exatl account o f the days and hours of the birth o f
each generation. He then difcovered both males and females
among them, whofe amours were not in the leaft equivocal; the
males are produced only in the tenth generation, and are but few
in number; drat thefe foon arriving at their full growth, copulate
with the females, and that the virtue o f this copulation ferves for
ten fucceffive generations; that all thefe generations, except the
firft, from fecundated eggs are produced viviparous, and all the
individuals are females, except thofe o f the lafl generation, among
whom fome males appear to lay the foundation o f a. frefh feries.
In,
In order to give a further infight into the nature o f thefe infefts-,
I {hall infert an extract of a defcription o f the different generations
®f them by Dr. Richardfon, as publilhed in the Philofophical
Tranfactions, vol. Ixi.
The great variety of fpecies which occur in the infefts now
under, confideration, may make an inquiry into their particular
natures feem not alitde perplexing, but by reducing them under
their proper genus, the difficulty is confiderably diminiffied. We
may reafonably fuppofe all the infects, comprehended under any
diftinft genus, to partake of one general nature ; and. by diligently
examining any particular fpecies, may thence gain feme infight
into the nature of all the reft. With this view Dr. Richardfon
chofe out of the-various forts, o f aphides the largeft o f thofe found
on the rofe tree, not only as it’s fize makes- it the more con-
fpicuous, but as there are few others o f fo long a duration. This
fort appears early in the fpring, and continues late in the autumn;
while feveral are limited to a much fhorter term, in conformity
to the different trees and plants from whence they draw their
nouriflmient.-
1 j f at the beginning ofTebruary the weather happens to be
fo warm * s to make the buds of the rofe tree fwell and appear
green, fmall aphides are frequently to be found on them, though
not larger than the y.oung ones in fummer, when firft produced.
It will be found, that thofe aphides which appear only in fpring;
proceed from fmall black oval eggs, which were depofued on the
laft year’s {hoot; though when it happens that the infeHs make
too early an appearance, the greater part fuffer from the {harp
weather that ufually fucceeds; by which means, the rofe trees
are.