230 NATURAL HISTORY OF WASPS, 
not the undigested residue of food, for it lies outside 
the cocoon, and must therefore have been deposited 
there before the larva had begun to weave this, and 
had cast its second skin, before therefore the bowel 
of the larva has become pervious. Besides, the 
deposit lies loose, not enveloped m a membrane, as 
the contents of the intestines of the larva would 
have been. The absence of uric acid supplies an- 
other—however slight—argument in favour of the 
conclusion that this deposit never passed through 
the intestines. It is very small in quantity compared 
with the dark mass which encroaches so sensibly on 
the depth of the wasps’ cell. 
The thickest part of the cocoon of the wasp is at 
the cap, in connection probably with the fact that 
the faculty of making silk continues to be an attri- 
bute of the perfect wasp, while the bee only makes 
silk this once in her life. On the contrary, the 
bottom of the bee’s cocoon is the thickest part of 
her flimsy structure. Held in shape by the adherent 
pollen granules, it seems to be thicker than it really 
is in this place. As the bee-larva grows its power 
of making silk gradually fails, and the cap of the 
cocoon is so thin that the workers have to make 
good the deficiency by plastering this end over with 
wax. Otherwise the pupa would be dried up within 
her case. It is curious to notice how one thing 
compensates for another; the wax cell-walls, and 
the elder sisters at hand to stop the pervious end of 
the cocoon with wax, make up for the shghtness and 
deficiencies of the work of the larva. 
The number of the successive tenants of a bee’s- 
cell may be most easily counted at the bottom, where 
