iv SOCIAL HOMES 151 



and their remarkable architecture has been allowed 

 to pass without the investigation that it merits. 

 Among kinds neglected must be included species of 

 Crematogaster. When these run about they hold 

 their abdomen high in the air, so that it curves 

 backwards and overhangs the thorax, whence is 

 derived their title signifying "hanging-belly." In 

 the Brazils a species popularly called the Negro 

 Head makes a strange nest, as round as the negro's 

 bullet-shaped head, and exteriorly covered with pro- 

 jections, suggestive with a little stretch of the imagi- 

 nation of the African's close woolly hair. It is 

 pensile on trees, and might easily be mistaken for 

 the pensile home of certain wasps. Its internal 

 arrangements prove to be more elaborate, for it is 

 ramified with multitudinous covered passages inter- 

 lacing intricately, but all leading to the interior cells. 

 Formica elata and Myrmica kirbii also carry their 

 abdomens erect, and both build on the branches of 

 trees and shrubs. The nest of the former is a wonder- 

 ful construction of earth mixed with leaves, which in 

 some cases are exchanged for minute vegetable 

 hairs. Myrmica kirbii makes a habitation of a 

 congeries* of the excrement of cows and mules 

 spread out into a multitude of thin folia, which are 

 placed one upon the other in a wavy or scalloped 

 manner, like the tiles of a house, leaving numerous 

 arched entrances beneath the flakes, so that although 

 the insects can creep into the nest, no water can 

 enter. Over the summit is stretched a very large 

 flake in one unbroken sheet, like a skull-cap on a 

 man's head, which acts as a general roof and projects 



