266 INSECTA. 
ded transversely in the manner of a ring, or which are 
even composed of five very distinct joints; but the sucker is 
formed of only four pieces, and the proboscis, the stem of 
which is usually very short, is almost entirely retracted within 
the oral cavity. The membranous nature of that organ and 
its turned up lips, its similarly raised and clavate palpi, the 
relative disposition of the wings which are usually crossed, 
the form of the abdomen which is rather oval or orbicular 
than triangular, and finally the scutellum which is frequently 
armed with teeth or spines, also distinguish the Notacantha 
from the Tabanides. 
But few of their larvee have been observed. Such as have 
been discovered, are described and figured by Swammer- 
dam, Reaumur and Reese], are aquatic, and approximate to 
those of the Athericera in their soft head, varying in form, 
and in their habit of becoming pupx under their own skin; 
but they retain their primitive form and proportions, thus 
differing from those of the latter. 
Other larvee of the Notacantha—Aylophagus—live in the 
carious and diseased parts of trees. 
We divide the Notacantha into three principal sections. 
Those of the first—JZydasii, Lat.—never have teeth or 
spines in the scutellum. ‘Their body is oblong, and the ab- 
domen forms an elongated and conical triangle. ‘The wings 
are distant. ‘Their antenne, from which we draw their most 
distinguishing character, are sometimes composed of five dis- 
tinct joints, the two last of which form a club in some, and 
the extremity of a cylindrical stem with a subulate termina- 
tion in others, and sometimes of three joints, the last of which 
is largest, almost cylindrical, tapers to a point and is divided 
into three annuli; thus these organs are always divided into 
five. With the exception of Mydas in which the vestige of 
a very small stilet is perceptible, neither that appendage nor 
the seta-which replaces it can be found in any of the Nota- 
cantha of this section; it is possible that the two last joints 
may represent them. 
In some the antenne are much longer than the head, con- 
