ANATOMY AND PHYSIOLOGY. 79 
the other face, we shall find it hollowed out on the 
inside, swelling up towards the articular extremity, 
but thinned off to the cutting edge. And it must 
be indeed a cutting edge when worked by its power- 
ful muscles. For, besides the points which show on 
the outside, there is another set of cusps within, 
separated from the former by a channel like that 
which runs between the teeth of a double toothed 
pocket-saw, or, coming nearer home, between the 
outer and inner row of the cusps of our own upper 
molar teeth. Wasps have no gizzard, no cutting or 
grinding instrument such as crickets and cockroaches 
possess, placed further in to break up any refractory 
morsels of food. Whatever is to be done in this way 
must be done here by the mandibles. But wasps live 
mostly on pulpy matter or juices, they do not triturate 
hard substances into a digestible mass, they only 
break them down to get at the nutritive material 
which these contain. So their jaws are fitted with 
teeth rather for cutting, tearing, and sawing, than for 
grinding, like a dog’s rather than a horse’s; they are 
_ for collecting materials rather than for masticating 
food, and are shaped accordingly. 
We have yet to examine the most complex portion 
of the mouth, the labium and maxille. As these 
parts supply very important specific distinctions, it is 
useful to be able to remove them for examination 
without disfiguring the specimen. This can be readily 
effected, in a recent or a moistened specimen, by 
gentle manipulation with a needle behind the man- 
dibles. With care, a mass can be removed, in which 
we shall find the labium and maxille entire and in 
their natural connection. And, in the absence of the 
