152 PLANT LICE. 
feelers are short, five- or six-jointed; the beak is variable in 
length; the eyes are very small and inconspicuous, or are en- 
tirely lacking; the legs are short and stout; the tarsi possess two 
claws, which are sometimes folded so as to appear single, or there 
is only one claw, as in the genus Rhizobius. There are no honey- 
tubes, yet the insects are always accompanied by ants. These 
lice have commonly a depressed form, tinted with pale brown or 
yellow colors; they are found upon the roots of plants, where 
they can become very destructive. 
Rhizobius lactuce Fitch. (The Lettuce Earth-louse). 
This eastern species sometimes occurs in destructive num- 
bers on the roots of the lettuce, both on wild and cultivated kinds. 
It measures less than one-tenth of an inch in length, is oval, of 
a dull white color, with dusky legs and feelers. The whole body 
seems to be dusted with a white powder. 
Roots of grasses like those of Poa and Eleusine, and the 
roots of other herbaceous plants, harbor such insects, even some 
evergreens do not escape. 
The genus Tychea, which belongs to this sub-family, is found 
in Minnesota, and Prof. Oestlund has described one species oc- 
curring on the roots of a common weed, the Ambrosia trifida. 
The genus possesses five-jointed feelers, of which the third joint 
is the longest. 
Tychea phaseoli Passerini. (The Bean Root-louse). 
Prof. Garman has described this insect as being quite de- 
structive to cultivated beans in the gardens near Lexington, Ky. 
It was so numerous, clustering on the root-stalks, that it was 
difficult to get a stand of plants. It is illustrated in Fig. 140, 
is almost globose in shape, and has the body clothed everywhere 
with short, erect pubescence. Living specimens are white, owing 
to a coat of waxy material, but if this coat is removed it is seen 
that the real color is pale yellow, nor is this waxy material found 
in the young lice, which have a glossy honey-yellow color; the 
tips of the feelers and the tip of the beak, as well as much of 
the legs, are dusky. 
Plants infested by such root-lice have an irregular growth 
and dwarfed appearance. Whenever they occur we find little 
