550 Wisconsin Academy of Sciences, Arts, and Letters . 
to settle this question decisively was considered to be outside 
of the scope of this article, in which only the morphology of 
the parts is discussed. 
THE MOUTH-PARTS OF COLEOPTERA. 
The mouth-parts and the legs of insects are homodynamous, 
both originating as segmental appendages, the former of the 
head, the latter of the thoracic region. It is in the order of 
Orthoptera that we find conditions as regards the trophi more 
nearly approaching those of the original type than in any other 
order of insects. Next as to primitiveness come the Coleoptera, 
in most of which the sclerites of the trophi can be directly 
traced to, and recognized by comparison with, those of the Or¬ 
thoptera, and in some cases the conditions existing in the for¬ 
mer are the more primitive. 
In general, the maxillae are the parts which have undergone 
the least reduction and in which the sclerites are most dis¬ 
tinctly visible; the other trophi are generally compared with 
them. 
The mouth-parts consist of three paired and two unpaired 
pieces: the labrum, with the epipharynx; the mandibles; 
the maxillae or first maxillae; the labium or second maxillae; 
the hypopharynx (endo-labium). Of these, the mandibles, max¬ 
illae and labium are paired appendages of the head-segments; 
the labrum with the epipharynx, and the hypopharynx are not 
paired. 
The labrum or upper lip. This is not a true appendage 
and is unpaired in origin, arising in the embryo between the 
two halves of the brain (protocerebrum), while all the true 
appendages arise on each side of the nervous system (7). It 
forms the roof of the anterior part of the mouth and is gen¬ 
erally movably connected with the clypeus. Kolbe (5) claims 
a paired origin for the labrum. He says:— “Am Embryo 
mehrerer Insekten wiirde das ITervorgehen der Oberlippe aus 
zwei urspriinglich getrennten, Anhangspaarenahnlichen Ge- 
bilden nachgewiesen;” but he neither gives any figures nor 
cites any literature to support this claim. 
