RELATIONS AND SURROUNDINGS. 



145 



1 60. Parasitism. Parasitism is an association of indi- 

 viduals of different species in which one member (the 

 parasite) gets all the benefit and the other (the host) 

 suffers the loss. Parasitism combines some of the qualities 



FIG. 33. Larvae of bot-fly (Gastrophilus equf) in the stomach of the horse. 

 One-half natural size. From Luggar. 



Questions on the Figure. What can you find of the habits of the 

 bot-fly? Where are the eggs deposited? How do the larvae find 

 their way into the stomach? How do they pass from this to the 

 adult condition? How does the larva retain its position in the 

 stomach of the host? What term would properly describe this 

 kind of parasitism ? 



of commensalism and the preying habit. It is a kind of 

 slow preying. 



Parasites are of two kinds: external, as the fleas, lice, 

 and the like; or internal, as most of the parasitic worms. 



