122 Mr. G. R. Waterhouse on the 
ring after ring of mud, till the cell is closed in by a lid; the lid is 
excavated and rendered concave on its outer or upper surface, 
and is convex and rough on its inner surface, and, in fact, is 
a simple repetition of the first-formed portion of the cell, a 
part of a hollow sphere; and if the work proceeded beyond 
this point, there can be little doubt that this lid of a cell would 
become the bottom of another similar cell, and thus we should 
have the cells joined end to end, and with a common straight 
axis, as we see in the cells of certain other bees—Megachile for 
instance; here, however, the cells are deposited in cylindrical 
burrows made in the ground, and the cells themselves are cylin- 
drical. I have witnessed the construction of the first part of the 
cell of the Osmia, and I have seen cells in all states of progress 
from that part to their completion. The completed Osmia cell 
strongly reminded me of the isolated cells built by the hive-bee 
for the queen-bee larva; the general form is the same to this 
extent,—they are both hemispherical at the base, and gradually 
approach the cylindrical form towards the mouth of the cell. 
I have still one other form of cell, to which I wish to direct 
your attention. These two cells, like those of the Osmia, are 
constructed of mud, but the insect that formed them (a species of 
Eumenes) belongs to the wasp tribe. Whilst the Osmia is a short 
stout insect with short legs, the Humenes is slender and has long 
legs. The cell of the Osmia would be completely filled by the 
pupa of the insect reared in it; but that of the Eumenes is much 
larger when compared with the size of the insect that constructed 
it. This difference in the proportionate size of the cells has, no 
doubt, reference to the kind of food which has to be stored up 
for feeding the larva. Furthermore, these cells differ from those 
of the Osmia in being almost perfectly spherical. They remind 
one of certain water bottles, and, like them, have a short neck, 
through which is the opening into the nest. The opening is very 
small, but I have little doubt would permit the insect to enter the 
cell; but, on the other hand, I much doubt whether she could 
perform the whole of the work of its construction from the outer 
side. I believe, indeed, that in executing the latter part of the 
work, at least, the insect was inside the cell. However this may 
be, here is a cell, the foundation of which was laid down in seg- 
ments of circles of much larger size than those seen in the cell of 
the Osmia, and, in connexion with this, we have the fact, that 
the comparatively long legs of the Humenes would give it the 
power of a far greater stretch, supposing that her work was com- 
