56 
BEITISH APHIDES. 
De Geer’s treatise on ApMdes contains tlie descrip- 
tion of eighteen species. It is illustrated by engrav- 
ings which, though coarse, nevertheless have about 
them a certain truthfulness of character — ^particularly 
those which represent the* pseudo-galls on the spruce- 
fir, which he calls galle de sajpin and galle en pomme 
de sajpin. Except in a slight and general way he does 
not investigate the phenomena connected with the 
impregnation of Aphides. 
Linngeus, in his ' Systema I^aturse,’ briefly describes 
thirty-three species. In a note made by himself on the 
margin of his own copy, preserved in the library of the 
Linngean Society of London, he remarks that Aphides 
produce Zwe young in the summer, but that in the autumn 
they lay eggs, adding, A copula parentum foecundas 
nasci Alias, neptes, proneptes, abneptes, asseverunt En- 
tomologi.” Further on he says that they excrete honey- 
dew rorem melleum ”) from their two posterior 
cornua, and then he exclaims, ‘‘Hse formicarum vaccse 1” 
Linnseus does not appear to have made special experi- 
ments on Aphides^ but he notices a few of the more 
obvious characters of those species which came under 
his observation. By these descriptions some few 
species may be well recognised, but now it is difficult 
to determine from such short notices the identity of 
other forms he named. The same unfortunate brevity 
is to be found in the writings of Fabricius when treating 
on this family. He gives, indeed, little more than details 
of their general colour and their habitats, omitting alto- 
gether reference to the component parts of their 
antennoB and the varied structure of their wings. 
Schrank more exactly describes sixty species, for 
distinguishing which he relies a great deal upon the 
relative lengths of the antennse and the peculiar cha- 
racters of the tail and cornicles. As his descriptions 
are too brief to help much in identifying his species, 
he left much to be accomplished by future systematists. 
He ascribes too much value to colour, and in a great 
measure often fails to discriminate between the often 
