54 
BRITISH APHIDES. 
on ‘‘les pucerons” he more particularly investigated the 
history of ‘Me puceron du pin” [Lachnus pini) and “ le 
puceron du rosier” {Siphonophora tosce).^ He groups 
Aphides into two kinds, viz. those which live in com- 
panies without producing distortion of the leaves, and 
those which either form vesicular vegetable excres- 
cences or elaborate gall-like masses from the leaves. 
In this artificial classification he followed Keaumur. 
But whilst Reaumur to the last doubted the fact that 
real eggs were deposited by Aphides, and indeed 
believed that the elastic oblong bodies found in late 
autumn were only abortive embryos. He Geer held 
with Lyonet and Bonnet that they were truly ova. In 
summer he showed that Aphides were viviparous, and 
that they only became oviparous towards the end of 
the year. In the case of “ Aphis nuda pini ” he saw 
the polished egg deposited in September from the 
conical and attenuated tail of the wingless female. The 
mother of this species measured k5 lines, and the egg 
in its longest axis measured 0*75 line. His astonish- 
ment was raised at this disproportionate size, for the 
egg equalled one half the length of the body of the 
mother. He calls it “ un oeuf assez gros, et qui semble 
lui devoir causer assez de peine avant que de pouvoir 
sortir.” In due time he saw some of these eggs hatch, 
and thus he— at any rate for the time — set at rest the 
doubts raised by Reaumur. 
In the month of September De Geer also saw the 
union of the oviparous female of le puceron du pin with 
the apterous male. He says the male of this species 
has the same colour as the female, but it is smaller in 
all its proportions. Some species of Aphides he found 
to be wonderfully prolific in oviposition. He exam- 
ples the birch Aphis, the eggs of which he counted 
up to the number of 1500. They were all attached to a 
single birch twig {Betula alba), and seem to have been 
the produce of one female. He notes that a deep 
* ‘ Memoires pour servir a I’Histoire des Insectes,’ par De Geer. 
1778. 
