76 NATURAL HISTORY OF WASPS. 
readily available distinctions. Still, these parts of 
the mouth will repay a careful study, as well on 
account of their physiological importance, as for the 
sake of the unerring differential characters which 
scientific examination finds in them. 
The mouth of the Wasp, and of the Vespe in par- 
ticular, furnishes a very good illustration of the 
mandibulate or masticating form of the organ, where 
no single part is enlarged or diminished very dispro- 
portionately to the rest. It is very difficult to make 
a symmetrical microscopic preparation of the whole 
oral apparatus, as the parts are of such different 
degrees of thickness and hardness, and require such 
different modes of treatment to show them to the 
best advantage. But they may be seen in detail, 
and their description may be followed with the 
greatest ease, if they are merely loosely spread out 
on a slide with a little glycerine. 
The mandibulate form of mouth, as displayed in 
our wasps, is made up of the following parts. There 
is an upper lip, the labrum, which is a simple scale 
having a vertical plane of movement and a lower lip, 
the labrum, which has a corresponding direction of 
movement, but is of a more complex structure. 
Fig. 1.—Diagram of the several parts 
of the mouth of the wasp.’ 
a, labium with the four-lobed tongue and 
the two labial palpi. 
b, maxilla of one side, the basilar portions 
bearing at one end the cardo, at the 
other the hairy galea and the maxil- 
lary palpus. 
c, labrum. 
d, mandible of one side. 
