207 
indicate the specific relationship better than any other charac- 
ters. They are also of value for generic purposes and, so far 
as I have observed, are of use in the separation of families. By 
the study of these organs I believe that we shall eventually 
have a much better idea of the relationship of the families than 
we have at present. 
The female genitalia may have equally good characters, but 
my knowledge of these at present is too limited to allow me to 
generalize upon them. I hope to be able to do so at a later date. 
The only generalization I can make at present is the distinction 
between complete and incomplete ovipositors. 
Among the Fulgoroidea some of the chief characters used 
for generic purposes are the shape of the head and thorax and 
the number and arrangement of the carinae upon them. ‘These 
characters, I believe, are liable to independent origin in different 
species, and so some of our genera may have a polyphyletic 
origin. Some of the families as they now stand are also likely 
to have a polyphyletic origin. The further study of the male 
genitalia is likely to show this, and will lay the foundation upon 
which a more natural grouping of both species and genera is 
likely to be erected. 
THE OrpdER HEMIPTERA, 
The Order Hemiptera or Rhynchota forms a large, homo- 
geneous, and monophyletic group of insects characterized by the 
shape, position, development, and function of the mouth organs. 
Although there exists some difference of opinion as to the 
minor details of the homologies of the head and mouth parts, 
the fact has been established by embryological studies that they 
are built upon a normal, mandibular type, and that the altera- 
tion takes place during the development of the embryo. It has 
also been shown that the mouth parts arise in a similar manner 
in both the Homoptera and Heteroptera. 
The mandibles form long, thin setae; the maxillae during 
their development divide into two parts, one forming a long, thin 
seta and the other amalgamates with the head capsule; the labium 
is long and narrow, with its lateral edges curved upward, and 
meet together on the middle dorsal line, thus forming a split 
tube in which the setae rest. In the embryo the labium arises 
