308 A BOOK OF INSECTS 



their very building materials to a digestive process, but 

 they actually eat the same food over and over again, and 

 maintain a spotless cleanliness in their habitations by the 

 simple process of devouring all refuse matter, including 

 the cast skins of their young. There can be little doubt 

 that these strange habits are due to the fact that the 

 termites' staple article of diet — i.e. dead wood — is poor in 

 nitrogen, and difficult to digest. There is no margin for 

 waste or for neglecting any opportunity to feed. In this 

 connection it is interesting to note that certain species of 

 termites, like the South American leaf-cutting ants, grow 

 a kind of fungus. The workers heap up spongy, yellow- 

 ish masses of wood pulp in the larger apartments of the 

 nest ; and these masses soon become plentifully sprinkled 

 with a small, white fungoid growth of a peculiar kind, 

 apparently induced by termite cultivation. The fungus 

 extracts from the wood pulp its nitrogenous matter, and 

 the insects thus secure a supply of concentrated food, 

 which is said to be employed chiefly for nourishing the 

 younger members of the community. When a portion of 

 prepared wood pulp, or "mushroom cake," as it has been 

 called, becomes exhausted, it is removed, and replaced by 

 a fresh supply. The workers of one African species of 

 termite have been observed to issue from the nest at high 

 noon to cut and carry pieces of grass and leaves, and there 

 can be little doubt that this material is also employed for 

 fungus-growing. These workers, as well as their com- 

 panion soldiers, have faceted eyes ; whereas in most other 

 species all but the royal castes are quite blind. Some 

 termites actually feed upon the secretions of their own 

 salivary glands, or those of their companions. A tiny 

 globule of liquid appears in the mouth, and when it has 

 increased to about one millimetre in diameter, it is either 

 swallowed, used for building purposes, or — if the termite 



