INTRODUCTION. 
There is scarcely an individual, old or young, who has paid any 
ittention to plants during the summer, that has not observed upon the 
eaves or stems, twigs or bark, certain minute, soft-bodied insects, 
isually without wings and generally huddled together in little groups 
msily engaged in pumping the sap of the plant on which they are 
itationed. These insects, on account of their resemblance to certain 
>ther insects, and their parasitic habits have, by common consent, 
•eceived the very appropriate popular name Plant-Lice. Scarcely a 
fiant in the vegetable or dower garden; a bush, tree or vine in the 
rard, orchard, nursery, grove or forest; a worthless weed or variety of 
p-ass, but what at some time appears to be infested by them. Leaves, 
lower-stalks, twigs, stems and even the roots are at some time com¬ 
piled to furnish these insects food. Yet, notwithstanding their very 
general distribution and constant presence during the summer in almost 
;very garden, yard, orchard and grove, but comparatively little attention 
ippears to have been paid to them in this country. Even our ento- 
nologists appear to have generally passed them by with but little 
lotice, and although it is probable our species will ultimately be 
lumbered by the hundreds, yet up to within the last two or three 
rears scarcely a score had been described and named. One reason for 
his neglect probably arises from the fact of the difficulty of preserv- 
ng species for subsequent examination, and that but few systematic 
vorks on the family had appeared in Europe. 
I One reason why so little notice has been paid to them in works on 
economic entomology, is probably because of the supposition of their 
,'reat similarity in habits, and that a remedy applicable to 
me species would be equally applicable to all the 
)thers.- But what has been found to be' true in reference to other 
groups of insects is to a certain extent at least true of these, that the 
nore carefully we study them, and the more we find out in reference 
o their history and habits, the better qualified are we to counteract and 
iontrol them, and the more effectual will be the remedies which we 
vill be able to suggest. 
In order to illustrate the correctness of these remarks we have only 
o refer to the investigations in reference to a single species, the 
Irape Phylloxera, (Phylloxera vitifolm Pitch.) which engaged the atten- 
ion of some of the ablest entomologists both of Europe and America 
■everal years before its life history was thoroughly ascertained. My 
tudy of our Aphides for a few years, has sufficed to con vice me that as 
ret we are but upon the threshold of their biological history, that 
vhat has been ascertained in reference to them is but a small fraction 
>f that which is yet to be learned. 
