258 
STRANGE DWELLINGS . 
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, however, is very much longer 
in proportion to its width, and being fixed throughout its length 
to a leaf, is not so plainly visible as the last-mentioned specimen. 
Indeed, when the leaf has withered, as is the case with the object 
from which the drawing was made, the dull brown of the nest 
coincides so completely with the colour of the faded leaf, that 
many persons would overlook it unless their attention were 
specially drawn towards it. 
On the extreme right of the illustration, and in the upper 
corner, is seen a nest which is also the work of insects 
belonging to the genus Polybia, and it is pendent from a 
bough, like the habitation of the Chartergus and other pensile 
hymenoptera. 
In the same collection there are many more specimens of social 
nests formed by insects belonging to this genus, two cases being 
quite filled with them. One is attached to the bark of a tree, 
and resembles it so closely that it seems to be made of the same 
substance, this similarity of aspect being evidently intended 
as a preservative against the attacks of birds and other insect- 
loving creatures, which would break up the nest, and eat the im- 
