324 ANIMALS 



The greater part of the females remain undeveloped, and are the 

 workers. 



Ants, like bees, have a highly developed form of "society." Some 

 ants act as soldiers, and protect those that work. Certain ants cap- 

 ture other ants, and make them work. Other ants, still, have plant 

 lice for their "cows," and feed upon the liquids they produce. 



Some of the insects, such as the bees and the larvae of the silk- 

 worm, are useful to man; but others, like the mosquito and fly, are 

 only a nuisance and a danger (cf. 424). But in numbers the insects 

 and spiders probably exceed all other animals put together. 



340. Exercises. 



1. What is the oldest part of the clam's shell? Of the snail's? 

 Read a description of the chambered nautilus. Who wrote a poem 

 about it? 



2. What is the economic importance of the clam? From what are 

 pearl buttons made? What other materials are used for buttons? 



3. Why does the earthworm come to the surface after a heavy rain? 

 Show that the earthworm is the "original plowman." 



4. Why was an old-time doctor called a leech? 



5. Give a list of at least 5 insects that are hurtful to man or to his 

 domestic animals. Extend the list, if you can. 



6. Give a list of at least 5 insects that attack food plants or trees. 

 Extend the list if possible. 



7. Give the ways in which man protects plants from the ravages of 

 insects. (Cf. also 301.) 



8. Why are insects in the larva stage such greedy feeders? 



9. Out of what does the silkworm spin its cocoon? The spider its 

 web? From what does the bee get its wax? Its honey? 



10. How are insects helpful to plants? (Cf. 319.) 



11. What is cochineal? What is its source? Its use? Answer 

 the same questions for sepia; for ambergris. 



341. Fishes. The most striking difference between 

 fishes and all the animals already studied is that fishes 

 have an interior bony framework that supports the 



