HYMENOPTERA. 83 
and insensibly degenerates into a tube, the subdivisions of 
which are lost in the head. Behind these two abdominal ve- 
sicles, the organ of respiration continues on in two filiform 
tubes, giving off an infinity of ramous branches, and becoming 
confluent near the anus. In the Xylocope and Bombi, the 
anterior superior surface of each of the two great abdominal 
vesicles is furnished with a cylindrical, elastic, greyish body, 
but adhering throughout its length in the Xylocopz, and free 
in the Bombi. M. Dufour thinks that this body, which is 
directed towards the insertion of the wing, has some part in 
the production of the humming noise made by these Insects, 
inasmuch as that sound may continue after the wings have 
been taken off. 
I will divide this order into two sections. 
The first, or that of the TEREBRANTIA, is characterized 
by the presence of an ovipositor in the females. 
I divide this section into two great families. 
FAMILY I. 
SECURIFERA. 
Our first family is distinguished from the following ones by 
a sessile abdomen, or the base of which is joined to the thorax 
throughout its whole thickness, that seems to be a continua- 
tion of it and to have no separate motion(1). 
The females are provided with an ovipositor that is most 
commonly serrated, and which not only enables them to de- 
posit their eggs, but likewise to prepare a place for their re- 
ception. The larve always have six squamous feet, and fre- 
quently others that are membranous. 
(1) The segment, bearing the inferior wings, is separated from the following 
one or the first of the abdomen, by a transverse incisure or articulation. The 
other segments then follow uninterruptedly, and without any particular strangu- 
lation. 
