78 NATURAL HISTORY OF WASPS. 
The mandibles are moved by a very powerful mass 
of muscle which lies just behind the compound eye on 
either side, occupying the greater part of the side 
of the head. If we break this part of the head open 
the dried muscle falls out. It is a mass of fibres, 
converging from the inside of the rim which surrounds 
the face, to a tendon which is inserted into the 
mandible at its articular extremity. The bulk of the 
muscle offers a sufficient explanation of the amount 
of work that a hornet can get through. 
The articular surfaces are broad, and set in such a 
direction as that the mandibles shall move in the 
plane of the face. In the hornet there is a little wider 
interspace between this jomt and the lower part of 
the compound eye, than is found in the smaller wasps. 
As a rule, the mandibles of the Solitary group come 
closer up to the eye than those of the Social, but this 
character is not very distinct m the Vespe. The 
main strength of the mandible lies in the long claw 
which forms the lower edge, coming direct from the 
joint to meet its fellow, tipped with two strong black 
teeth. In form, this is very like that which we 
see finishing off the little round black faces of the 
Odynert beneath, and which constitutes the whole 
mandible of this species. But as the hornet not only 
cuts and carries, but also moulds, a triangular piece 
is added for this purpose, shaped like a woodman’s 
axe, but with a serrated edge. It is this triangular 
piece which gives such length to the face of the 
hornet, as to that of the smaller social wasps, and 
which, indeed, is the chief part of the mandible that 
shows in front. 
If we turn the little fragment round, so as to show 
