PLANT LICE. ilSjil 
from near the base to the tip of the wing, is the subcostal or 
submarginal one. The distal end of this vein becomes widened, 
and extends to the margin of the wing; this part of it is the 
stigma (st). From the stigma, a curved vein extends to the 
tip of the wing; this is the stigmatic or fourth vein. From the 
submarginal vein there branch two or three veins (in addition 
to the stigmatic vein), which extend across the disk of the wing; 
these are the first, second, and third discoidal veins. The third 
discoidal vein is sometimes forked. The veins of the hind wing, 
so far as they are present, are named in a similar manner. 
A. Winged form known; species not subter- 
ranean, except in a few cases where there 
are dimorphic forms. 
B. Front wings with three discoidal veins; 
antenne of the winged individuals, and 
generally of the apterous individuals, 
six- or seven-jointed. 
C. Front wings with the third discoidal 
vein twice forked; posterior wings 
with two discoidal veins; honey- 
TUNMCS VALIOUS eee cian te ere ars Seeas eee 4. APHIDINA. 
CC. Third discoidal vein with one fork or 
simple; posterior wings with one 
or two oblique veins; honey-tubes 
tuberculiform or wanting.........3. PEMPHIGINA. 
BB. Front wings with but two discoidal veins, 
the third being absent; antennz never 
more than five-jointed, sometimes but 
Pinee sj @liite dats wes ta ny seeeaeo or Se ts 2. CHERMESINA. 
AA. Permanently apterous; at least no winged 
form has been observed: chiefly subter- 
ranean, residing on the roots of plants.... I. RHIZOBIINA. 
SUB-FAMILY RHIZOBIINA, 
(Root-lice). 
This is a sub-family of plant lice in which no winged forms 
have thus far been found. They may be simply degraded wing- 
less generations of higher developed forms with wings. Their 
