1927] 
The North American Species of Ryhaxis 
219 
writer of available Rybaxis material shows that the problem is 
not quite so simple as at first supposed, for instead of having to 
do with two species only, I have discovered that we have at least 
half a dozen species that pass under the old names, of which 
several satisfy about equally well the descriptions of conjunda 
and clavata. 
Obviously, before further progress can be made, it becomes 
necessary to determine just what conjunda and clavata really 
are. This has been done with the highest degree of probability 
possible by a critical study of the respective series under these 
names in the Le Conte and Brendel collections. As a result of 
this determination, conjunda and clavata, supposed by Schwarz 
to be identical, prove to be quite distinct species. 
All our species of Rybaxis are superficially very similar, 
and for the most part are only recognizable with certainty by the 
secondary sexual characters of the males, the females by them- 
selves being often indeterminable. In all our species the males 
have the anterior tibiae acutely dentate within above the middle, 
and in most of them the antennal Club is enlarged and other- 
wise modified, and the anterior trochanters are apically spined or 
toothed in this sex. In addition to these characters, all of which 
are given in the books, the early descriptions of conjunda( 1850) 
and clavata (1866) record the presence in the male of acute meta- 
sternal processes. These are usually invisible in mounted spe- 
cimens, and both Le Conte and Brendel seem to have forgotten 
all about them, for they make no mention of them in their later 
writings when speaking of sexual characters nor do any sub- 
sequent authors appear to have noted their existence. 
In the examination of my material I have discovered still 
another and most remarkable structure which seems to be present 
with modifications in the males of all species of this genus, and 
which hitherto has apparently entirely escaped observation. This 
consists of a very small thin ligula arising perpendicularly from 
the rear margin of the second ventral segment for a short dis- 
tance, then abruptly bent forward and more or less expanded 
into a thin nearly horizontal plate, variable in form and size ac- 
cording to the species, and sometimes to a lesser degree indi- 
vidually. The form of this ventral plate, the position and form 
