26 SOCIAL HABITATIONS. 
as well as small in size, that they would not of themselves 
attract any attention. Their nests, however, are extremely 
interesting, as may be seen from the examples which are 
figured in the illustration. 
On the left hand may be seen a nearly spherical nest, 
which is evidently hollow, and has cells both on the out- 
side and within the cover. These cells are not placed 
vertically, with their mouths downward, like those of the 
wasp and hornet, nor horizontally like those of the bee, 
but are set with their mouths radiating from the centre of 
the nest. Moreover, there is another curious circumstance 
connected with the nest. Ifit were to be opened, it would 
be seen to be composed of several concentric layers, very 
much like those ivory puzzle-balls which the Chinese make 
so beautifully. 
The method by which the nest is formed is very simple, 
though not one that is usually seen among the hymenoptera. 
The layers of combs are made like hollow spheres, the 
mouths of the cells being outwards, and as soon as a layer 
is completed, the insects protect it from the weather by a 
cover of the same material as is used for the construction 
of the cells.) When they require to make a fresh layer of 
cells, they do not enlarge the cover, as is the case with the 
wasp and hornet, but place the new cells upon the surface 
of the cover, and make a fresh cover as soon as the comb 
is completed. Thus the nest increases by the addition of 
concentric layers, composed alternately of comb and cover. 
In the nest which is in the British Museum, the insects 
have commenced several patches of comb on the outside of 
the cover, and one such patch is shown in the illustration. 
On the right of the globular nest is another curious 
structure, also made by insects of the same genus, and 
having a kind of similarity in its aspect. This nest, how- 
ever, 1s very much longer in proportion to its width, and 
