300 A BOOK OF INSECTS 



or ten annually, but the numbers of the swarm augment 

 with the increase of the population." 



Termites also differ widely in the character of their 

 habitations. Some species, such as the yellow-necked 

 termite above referred to, dwell within the decayed 

 stumps and branches of trees, and their greatest archi- 

 tectural triumphs consist in a few barriers thrown across 

 the natural hollows of the wood. Others rear structures 

 so enormous that they profoundly modify the appearance 

 of the tropical landscape. The warlike termite builds 

 conical hills, which sometimes attain a height of from 6 

 to 10 feet, while the towers of certain Australian species 

 occasionally reach a height of 23 feet. The latter struc- 

 tures are very slender, and are supported with pilasters. 

 Another Australian termite, nicknamed by the officers 

 and men of H.M.S. Penguin the " compass ant," sets up 

 inverted, wedge-shaped masses of dark grey mud, from 

 4 to 5 feet high, which look like so many tombstones 

 in a churchyard. The strangest point about these erec- 

 tions, however, is the fact that they have invariably the 

 same orientation — the long faces of the wedge pointing 

 nearly north and south. Many species of termite build 

 hanging nests among the branches of trees ; but these are 

 usually, if not invariably, connected by covered passages 

 with subterranean galleries and chambers. 



Termites almost always approach the object of their 

 desire through tunnels, and are scarcely ever seen in the 

 open, although they roam over a wide area, and ascend 

 to the topmost branches of tall trees. Professor Drum- 

 mond gives the following description of the manner in 

 which these insects work : " At the foot of a tree the 

 tiniest hole cautiously opens in the ground close to the 

 bark. A small head appears with a grain of earth clasped 

 in its jaws. Against the tree trunk this earth grain is 



