
          309

"Our Insect Enemies". By Theodore Wood.
London, 1885.

From this book I quote as follows on

Dimorphism in Aphides:

"It is very likely that this singular fact of 
dimorphism may, when it is more thoroughly understood,
clear up for us many of the mysteries now
surrounding the life histories of certain aphides.
There are many species for example, with whose
doings we are acquainted  during a part only
of the year.  We find them busily engaged in
feeding perhaps for a period of six or eight weeks,
and then suddenly discover that they have
vanished, to appear no more until the following
season.  We cannot trace them during the 
intervening time.  We do not know whether
they go, on in what stage of development
they pass the winter.  All we have ascertained
is that they disappear from our [illegible]
for the greater part of the year, and we
have hitherto altogether failed to discover in
what manner and for what reason they do so.

"But if these species are dimorphous, the
difficulty is at an end.  Any of these aphides,
after appearing in one form for a month or two,
may then migrate,/ and show itself in a 
totally distinct shape upon a different
food plant etc." - pp. 51 and 52.

"The peach tree suffers very much from the attacks of
plant lice, which live under the leaves * * * Whether
our insect [there may be several of them] is the same as
the European aphis of the peach tree (Aphis Persicae of Sulzer)
I cannot determine for want of a proper description
of the latter."- p. 240 of 3rd Ed. of "A Treatise
on Some of the Insects Injurious to Vegetation"
By J. W. Harris. Boston, 1862.
        