THE INSECT WORLD. 



399 



dently keep the nest clean and remove decaying particles ; others 

 may be of some use to the ants by excreting certain sweet sub- 

 stances which induce their toleration ; while yet others have no 

 use at all, so far as we can discover. Such are certain crickets 

 which are always found associated with ants, and certain cater- 

 pillars. What functions these insects have in the ant-hills is as 

 yet somewhat obscure. 



In the tropics there are species that occasionally change their 

 camps, and are known as foraging ants. When the whim seizes, 

 or unknown causes determine them, they leave their nest, bag 

 and baggage, attended by all the insects that lived with them, 

 and start upon a march straight forward, destroying everything 

 that attempts to prevent their passage. A house or a village is 

 no barrier ; they pass through or over it, destroy every living 

 thing it contains, and devour all the provisions. The inhab- 

 itants of countries subject to these foraging expeditions soon 

 learn to recognize their character, and immediately seek safety 

 in flight. The ants continue their march, and soon the house 

 or village can be reoccupied, with the certainty that, if all the 

 provisions have been cleared out, so also have all the vermin : 

 rats, mice, snakes, roaches, and similar creatures being all killed 

 and eaten. 



The battles of ants have been described by more than one 

 author ; but as this is the function of another kind of work, 

 nothing more will be said here about these very interesting 

 creatures. 



Next in the orderly series come the Fossores, or "digger- 

 wasps." Here the two normal sexes only are developed, and 

 they are solitary, — that is, they never form communities. They 

 often build their nests underground, preferring sandy spots ; but 

 the families vary much in this respect. The females are always 

 provided with a sting, which they use on slight provocation, and 

 they differ from the next family of true wasps by having the 

 wings always flattened and never longitudinally folded in repose. 

 Sometimes, instead of burrowing underground to form their cells, 

 they use the stems of pithy plants like alder and sumach, and 

 often nests are built of mud, in sheltered localities against houses, 

 barns, or other convenient places, or even attached to twigs or 

 shrubs, 



