394 



Relations between Species 



duces a chain of cells in the form of a lasso in which a portion of a 

 nematode, or other soil microorganism, becomes ensnared and which 

 then tightens up sufficiently to kill the victim (Bessey, 1950). 



Some predators are restricted to one prey species or are dependent 

 upon a small group of food species, whereas others are highly catholic 

 in their tastes, as has already been discussed in Chapter 8. Con- 

 versely, certain prey species are attacked by only one predator, but 

 others may satisfy the appetites of many kinds of diners. The special 

 anatomical and physiological adaptations of predator species for 

 securing, devouring, and digesting specific prey species, and the 

 equally elaborate specializations of the prey to avoid detection or to 

 resist capture, have been considered in earlier chapters. 



Photo by B. W . Allied, U. S. Soil Conservation Service 



Fig. 10.13. A group of pitcher plants {Sarracenia flava) in swampy land of 



Louisiana. 



In some animals only the adults are predatory, whereas the young 

 are parasitic or live wholly upon the yolk supplied in the eggs. In 

 other animals, such as many insects, the larvae do most of the eating, 

 and in certain species the adults do not feed at all. Some predators 

 feed upon the adidt stage of their prey, some on the larvae, some on 

 the eggs, and some on more than one stage. If members of the prey 

 species are killed before they have had a chance to reproduce, the 



