PARASITISM 821 



for being fed so that the hosts appear content with their presence. 

 They are worse than commensals since they use up some of the food 

 supply of the colony. Other insects that actually eat larvae are toler- 

 ated and to some extent protected by the colony. This is predation 

 against the larvae, but in relation to the whole colony may be regarded 

 as a form of parasitism since the invaders remain with the colony and 

 do not kill it. 



Questions 



1. Give examples of ectoparasitism, intestinal parasitism, blood parasitism and intracel- 

 lular parasitism. 



2. Describe the evolutionary pathways by which an animal may become a parasite. 



3. Name an ectoparasite and an endoparasite which eat the flesh of man and describe the 

 life history of each. 



4. Discuss three adaptations common in parasites. 



5. Distinguish between biting and sucking lice according to both their ta.vonomy and 

 their hosts. 



6. Describe the life cycle of the common tick. 



7. Where are hookworms prevalent? What counter measures are effective against hook- 

 worms? 



Supplementary Reading 



Chandler, Introduction to Parasitology, is a standard text of the subject. Ecologic 

 aspects are discussed and many interesting examples are given in Ecology of Ani)nal Para- 

 sites by Baer. Many books are devoted entirely to the medical and clinical aspects of 

 human parasites. Rats, Lice and History by Zinsser is a popular and authoritative account 

 of typhus down through the ages. .\n excellent source book for tropical parasites is the 

 Manual of Tropical Diseases by Mackie, Hunter, and Worth. An excellent semipopular 

 account of parasitism is that of Rothschild and Clay, Fleas, Flukes, and Cuckoos. 



