165 
roots of plants. But it is more than probable that when the life 
history of the species is traced, it will be found that many of 
them produce winged individuals. In fact it may ultimately be found 
that no species is permanently apterous. 
So far but few species of this group have been determined in this 
country, and these have been assigned to two genera, Rhizobius and 
Tychea , but the characters by which the genera and species are dis¬ 
tinguished are so slight and uncertain that no great reliance is to be 
placed upon them except where the species have been observed with 
sufficient care to ascertain positively the adult state, and the habits. 
So far as my observations have extended the species, do not appear 
to be confined so rigidly to a given species or genus of plants as is 
the case with aerial species. This fact also adds to the difficulty of 
determining species. 
Genus 
RHIZOBIUS. 
Burm. 
I 
As I have no means of access at present to the original diagnosis 
of this genus by Burmiester I can only define it from the statements 
of others and from the species assigned to it. The characters by 
which it is distinguished by recent authors are as follows: 
Species apterous, at least so far known; subterranean, residing only 
on the roots of plants. Antennie very short, and according to Passe- 
rini six-jointed, according to Fitch, five (?) or six-jointed; but a species 
described beiow which I am pretty well satisfied belongs to this genus 
has these organs apparently seven-jointed, but the division between 
the third and fourth is not distinct; the joints are sub-equal, the third 
not obviously longer than the fourth, each short, the last usually the 
longest and thickest. Honey-tubes wanting. Tarsi with but a single 
claw, in the species so far described. 
Dr. Fitch states that the species are always viviparous and never 
oviparous, an assertion which cannot be accepted as correct without 
further proof. 
Rhizobius lact uCjE. Fitch. Lettuce Earth-louse. 
The young lice measure 0.02 in length, are very pale yellow, glossy 
and watery, with the legs and antennae whitish. They are nearly thrice 
as long as broad, somewhat flattened, their opposite sides parallel in 
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