11 
AA .—The four wings opaque, farinose, or covered with a powdery 
substance, resembling in general appearance minute moths; pupae in¬ 
active and scale-like. 3. Family —Aleurodidje. 
The third family is placed by quite a number of entomologists 
among the Cocddce or bark-lice, with which they agree in several im¬ 
portant respects. It evidently forms an intermediate group between 
the two divisions, and approaches about as near to one as the other; prac¬ 
tically it is of very little importance where it is placed, as there are 
no species belonging to the family that are sufficiently injurious to re¬ 
quire attention. 
By the most recent authorities as Buckton (Monograph of British 
Aphides ) Packard, (Guide to the Study of Insects) etc., this group is 
placed among the Coccidce or bark-lice. As I will have no occasion 
in the present brief account of our plant-lice, to allude to any species 
it, I will not discuss its position. 
The Psyllidce are not usually included in works devoted to plant- 
lice, but as there are some species known to be injurious to cultivated 
plants, I have concluded to give a short account of the family and 
the few species which haVe been observed in this country. 
The following is a copy of a “Key to Hemoptera” which I prepared 
for the use of my classes in entomology, and although perhaps not 
the best that could be devised, was nevertheless found quite useful in 
listinguishing the families of the order. 
( 
(Families according to Westwood.) 
[Sub-Orders.) 
I. Elytra uniform in texture, coriaceous or membranous: beak arising 
from the underside of the head. 
II. Elytra coriaceous at base; membranous at the apex; overlapping each 
other in repose; beak arising from the front of the head.I 
. Homoptera . 
Heteroptera. 
( Families .) 
HOMOPTERA. 
a Tarsi three-jointed; antennas minute, terminated by a slender bristle; 
wings areolate. 
b Antennre six or seven-jointed; three ocelli placed in a triangle on the 
back of the head; males musical. 
bb Antennae two or three-jointed, males not musical, 
c Antennae only distinctly three-jointed, inserted immediately beneath 
the eyes; the two ocelli placed beneath the eyes; head often ros¬ 
trate . 
Fulgoi'idac. 
cc Antennae apparently two-jointed, inserted in front between the eyes; 
head broad, triangular: the two ocelli placed on the face or fore¬ 
head (sometimes wanting); pronotum sometimes enlarged; and 
anomalous in form./. 
Cercopidac. 
aa Tarsi two-jointed; antennae six to ten-jointed, filiform, lai'ger than the 
head; the four wings transparent; beak apparently arising from 
the prosternum. 
d Antennae ten-jointed, terminated by two short bristles, basal joint thick_ Psylidac. 
dd Antennae three to seven-jointed, apex simple; abdomen with two, more or 
less, elongated tuburcles near the extremity.. Aphididm. 
aaa Tarsi one-jointed, terminated by a single claw; males with but two 
M __j__ j. i_i_<• __ i _ «** _ .a t • , /■ . -i 
wings and without beak; female' M apterous, changing to a footless 
scale on the plant it is attached to. 
Coccldae 
