OF INSECTS. 
307 
with the basal joint much dilated. Fam. Andrenidce , 
Apidai. 
In illustrating this order more in detail, we shall 
first select a characteristic example from the family of 
the Tenthredinidse.* 
Fam. Tenthredinidse. 
This extensive family may be known by having 
the abdomen sessile, or united by its whole breadth 
to the hinder part of the thorax, in such a manner, 
that it possesses but little power of separate move- 
ment. The maxillary palpi are always six- jointed ; 
the labial four-jointed ; labium trifid; wings ample, 
and provided with many complete cells ; females with 
an ovipositor. 
It is from the use and appearance of the instru- 
ment just named that these insects are called saiv- 
Jiies. It is placed at the extremity of the abdomen 
of the female, on the under side, and is so con- 
structed, that it combines the properties of a saw 
and auger. It consists of two plates of the same 
form and size as two external valves, which serve 
as a sheath to them, and enclose a short triangular 
* We purposely exclude from these illustrations the most 
interesting of all the hymenopterous families, the Apida, as 
their history is given, in a way commensurate with its impor- 
tance, in a separate volume. The details there afforded of 
this characteristic group are so ample, as to preclude the 
necessity of entering at such length into the generalities of 
the order in the above sketch, as it would otherwise have 
been necessary to do. 
