NO. 7 PROTECTIVE ADAPTATIONS McATEE I23 



commonly on toads and frogs in three separate in\estigations of its 

 food habits in Trinidad. 



Leeches prey upon both eggs and young of amphiljians and there 

 are numerous insects which destroy tadpoles. Such are the giant water 

 bugs, backswimmers, water scorpions, predacious diving beetles, and 

 their larvae, and tlie nymphs of dragonflies. Finally, it should be 

 mentioned that myriads of amphibian eggs and young perish because 

 of the unwise choice by their parents of too temporary bodies of 

 water for their egg-laying. 



Discussion. — The relations of {predators to amphibians throw an 

 interesting light on the efficiency of protective adaptations in averting 

 the attacks of foes. Clearly the Ranidae or frogs are more preyed 

 upon than any other group, certainly much more so than the toads. 

 The theorist on adaptations attril)utes this to the su]ierior special 

 defenses of toads, but with no dou1:)t whatever the difference in 

 amount of predation on these two groups is a direct reflection of their 

 relative abundance. 



If toads really were specially protected, if their so-called defenses 

 actually saved them from a certain proportion of ]:)redatory attacks, 

 should they not increase continually relative to the Ranidae? The fact 

 that they do not is the best proof that could be asked that their 

 " special defenses " do not actually function in nature. In short there 

 is no reason to believe in the case of amphibians but that the attacks 

 of predatory enemies bear a close relation to abundance and availa- 

 bility of the various orders and families. Where a certain group 

 appears to have an advantage in escaping certain foes, to a degree, it 

 invariably proves that it suffers extraordinarily from attacks of other 

 enemies. 



Reptilia (Turtles, Lizards, Snakes) 



Protective adaptations. — Although turtles have the direct defenses 

 of their shells, jaws and claws, several of the species have also a 

 strong musky odor, and some exhibit warning colors. Numerous 

 lizards have cryptic coloration ; one of our species is poisonous and 

 one has the faculty of changing its color considerably. Many lizards 

 drop their tails easily, a device said to aid them in eluding enemies. 

 The horned-toads besides their protective coloration have more or 

 less prominent spines on the back of the head. Many snakes exhibit 

 cryptic coloration and a number of them have offensively odorous 

 secretions. Certain serpents practice intimidatory actions and a con- 

 siderable number of our species are dangerously venomous. 



