62 Dr. Burnett on the Development of Viviparous Aphides. 
Art. VII.—Researches on the Development of Viviparous 
Aphides ; by Watvo I. Burnett, M.D., Boston. 
Every naturalist is aware of the remarkable phenomena con- 
nected with the viviparous reproduction of Aphides or plant-lice, 
or their singularity has led them to be recounted in works other 
than those of natural science, and, from the days of the earlier ob- 
servers, they have been the theme of a kind of wonder-story in 
zoology and physiology. 
I need not here go over the historical relations of this subject. 
The queer experiments and the amusing writings of the old Ento- 
mologists are well known. ‘The brief history of the general con- 
ditions of the development of these insects is as follows: In the 
early autumn the colonies of plant-lice are composed of both male 
and female individuals ; these pair, the males then die, and the 
females soon begin to deposit their eggs, after which they die also. 
Early in the ensuing spring, as soon as the sap begins to flow, 
these eggs are hatched, and the young lice immediately begin to 
pump up sap from the tender leaves and shoots, increase rapidly 
in size, and in a short time come to maturity. In this state it is 
found that the whole brood, without a single exception, consists 
solely of females, or rather and more properly, of individuals 
which are capable of reproducing their kind. This reproduction 
takes place by a viviparous generation, there being formed in the 
individuals in question, young lice which, when capable of enter- 
ing,upon individual life, escape from their progenitor and form a 
new and greatly increased colony. This second generation pur- 
sues the same course as the first, the individuals of which it is 
composed being like those of the first, sexless, or at least without 
any trace of the male sex throughout. These same conditions 
are then repeated, and so on almost indefinitely, experiments hav- 
ing shown that this power of reproduction under such cireum- 
stances may be exercised, according to Bonnet,* at least through 
nine generations, while Duvaut obtained thus, eleven generations 
in seven months, his experiments being curtailed at this stage, 
not by a failure of the reproductive power, but by the approach 
of winter which killed his specimens; and Kybert{ even observed 
that a colony of Aphis dianthi which had been brought into a 
constantly heated room, continued to propagate for four years, in 
this manner, without the intervention of males, and even in this 
instance it remains to be proved how much longer these phenom- 
ena might have been continued. 
The singularity of these results led to much incredulity as to 
their authenticity, and on this account the experiments were often 
* Bonnet, Traité d’'Insectologie, ou observations sur les Pucerons, 1745. 
+ Duvau, Mém. du Mus. d’Hist. Nat., xiii, p. 126. 
} Kyber, Germar’s Magaz. d, Entomol. 1812. 
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