ARACH N I PS , CENTIPEDES, AND MILLIPEDES— ARTHROPODS 209 



the embryonic development. Developing millipedes have only one pair 

 of legs per segment, but later the segments fuse in pairs so that the 

 adults show only one segment for two pairs of legs. Millipedes have no 

 fangs and are entirely harmless. 



Classification and Derivation of Scientific Words 



Phylum Arthropoda (Cont.) 



Class B. Arachnoidea. (Gr. arachne, spider). Spiders, scorpions, 



granddaddy longlegs, mites, ticks, and king crabs. 

 Class C. Chilopoda (Gr. chcle, claw; pons, foot). Centipedes. 

 Class D. Diplopoda (Gr. diploos, double; pons, foot). Millipedes. 



REVIEW QUESTIONS 



1. Describe respiration in the spiders. 



2. Discuss the uses of spider web by the spiders. 



3. Discuss the uses of spider web by man. 



4. Describe reproduction in a typical spider. 



5. How are young spiders distributed? 



6. How do scorpions differ from spiders in their method of injecting poison? 



7. Describe the activities of the itch and mange mites. 



8. Explain how germs may be transferred from one animal to another by ticks. 



9. What are the primary distinctions between the centipede and the millipede? 



10. Explain how it is that millepedes have two pairs of legs on each body seg- 

 ment, whereas arthropods generally have only one pair. 



11. Why is the house centipede of economic value? 



12. What are red spiders and how do they harm man ? 



13. Why is it thought that king crabs are closely related to the extinct Trilobita? 



14. How do chiggers obtain their food? 



15. Which is our most poisonous spider? How does its bite affect the human 



body ? 



16. Describe the two primary methods which spiders use to capture their food. 



17. How does a spider, without chewing mouth parts, obtain food through the 

 thick shell of an insect? 



