76 SOCIAL HABITATIONS. 
fresh importations should be made as fast as the demand 
for workers exceeds the supply; and it is really a won- 
derful thing that the Amazon Ants should always select 
the pup which will afterwards be developed into neuters, 
and never take those from which males or females will 
issue. 
The Amazon of the Continent is not the only Ant which 
enslaves the neuters of another species, for in different parts 
of the world several species of Ants have been observed 
which seize upon workers belonging to other nests, and 
bring them to do the work of the home. A Brazilian 
species has been observed to act in a similar manner. 
In the accompanying illustration are shown two remark- 
able nests, made by insects of the same genus, which have 
been placed side by side in order to show the different 
manner in which cells are arranged by insects which are 
closely allied to each other. 
The smaller, though more conspicuous nest, is formed by 
an insect which is called Polistes aterrima, a name which is 
very appropriate to the creature, inasmuch as the generic 
title signifies a builder, or the founder of a city, and the 
specific name signifies intense blackness, and is given to 
the insect on account of its colour. In general shape the 
insect resembles other species of its genus, but is rather 
larger than the generality of its kin, and is conspicuous 
for its deep black cvlour. 
The method of nidification which this species adopts is 
very peculiar. The cells are formed with beautiful regu- 
larity, but are arranged in a very curious fashion. They 
are placed with their mouths downwards, as is frequently 
the custom with the cells of hymenoptera, but are not quite 
perpendicular, inclining alternately to either side. Each 
cell is set rather lower than its predecessor, so that the 
