78 SOCIAL HABITATIONS. 
are about the same size as those of the curious clay nest 
which has already been described, but they are undefended 
by any covering, and exposed to the weather. 
It has been suggested by some observers that the combs 
might have been originally protected by an outer case, and 
that the case itself has been lost. The formation of the 
branch, however, from which the combs are hung, serves to 
militate against any such theory, as the twigs project so far 
that they must have been enveloped by the covering if it 
ever existed, while upon them there is no trace of any 
such material as that of which the nest is made. The in- 
ference is, therefore, that they were never intended to be 
protected by a cover, but that they were intentionally ex- 
posed to the air, as is the case with the habitations of 
Polistes and several allied insects, whose homes will 
shortly be described. 
One of the most curious points in the construction of 
this nest is the manner in which it is suspended to the 
branch. As is shown in the illustration, the combs are 
comparatively narrow at the point of attachment, and gra- 
dually increase in width, so that their weight, when filled 
with the young brood, must be considerable, and the strain 
on the upper part of the comb very great. The manner 
in which the insect has met this difficulty is really won- 
derful. It has not made the upper part of the comb to 
consist of a solid mass, as is the case with the clay nest 
which has just been described, but has utilised almost 
every portion of the comb from the top to the bottom. 
But, in order to obtain the needful strength, the upper 
part is constructed after a manner that is widely dif- 
ferent from that which prevails upon the lower and wider 
portion of the comb. 
If one of the combs were broken across, the lower half 
would much resemble, except in colour, the nest of an 
