OF INSECTS. 
297 
the Hymenoptera from the rest of their class, but 
it is necessary to describe the various parts more in 
detail. 
The head is not received into a cavity of the thorax, 
but is attached to it by a ligament, so flexible that 
the head can be almost turned round upon it. It 
is likewise capable of some extension, and the head 
has thereby considerable freedom of motion. The 
composite eyes are sometimes larger in the males 
than in the other sex. The stemmata are always 
three in number, commonly disposed in an equilateral 
triangle, but occasionally almost in a transverse line. 
In the organs of the mouth we can distinctly recog- 
nise mandibles, maxillae, lingua, labrum, labium, and 
palpi ; but these parts are so variously modified in 
different tribes, that a general definition of them will 
possess little value. The mandibles are strong and 
salient, usually toothed, and sometimes each blade 
appears as if formed by the union of two similar 
pieces. The maxillm are usually much developed, 
the blade or stipes often greatly elongated, and the 
insertion (the cardo or hinge of Kirby,) distinctly 
visible. The blade of the maxillee acts an important 
part in composing the tube in honey-sucking tribes. 
There are commonly two lobes at the extremity, 
which are sometimes acute, at other times very ob- 
tuse. The palpi attached to this blade are almost 
always long, and in the greater .number of instances 
contain six joints ; in the minute parasites, however, 
they are frequently abnormal, and often present only 
two articulations. The labium is much larger than 
