POLYBIA. 27 
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 tee 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 immature and 
tender grubs. Most of the nests are fixed to leaves, and 
are different forms, according to the species which made 
them. They are mostly fixed to the under sides of the leaf, 
so that the weight causes the leaf to bend and to form a 
natural roof above them. The shape of the nest seems to 
depend much on the character of the plant to which it is 
fixed. Those that are fastened to reeds are long and 
slender, and generally much narrower than the sword- 
shaped leaf on which they rest. Others, which are fastened 
to short and broad leaves, adapt themselves so closely to 
the shape of the leaf, that, if removed, they would enable 
any one to conjecture the form of the leaf upon which 
they had been fixed. 
One such nest is very remarkable. In general form it 
