I THE AMPHIBIA IN GENERAL 13 



a great clamor with their song. Then they disappear, and 

 may not again show themselves for several years.^ 



The Bufonidae, or toads, comprise a large family which 

 is found on all the continents of the globe. The principal 

 genus is Bufo, which includes the best-known representa- 

 tives of the family. The toads of this genus possess a very 

 rough, warty skin, whose irregularities are caused by the 

 large number of poison glands contained in it. These 

 glands secrete a whitish, milky fluid of a very poisonous 

 nature. Even a very small quantity of this substance when 

 injected into the blood of a small animal soon produces fatal 

 effects. The abundance of this secretion affords the toad 

 very efficient protection, and not many animals have the 

 hardihood to attack the creature. In addition to the poison 

 the skin secretes mucus, as in other amphibians, although 

 X not in great quantity. 



The color of toads, like that of frogs, may change under 

 the influence of different external conditions. When ex- 

 posed in a light-colored environment, the skin usually 

 becomes lighter in color. In a dark environment it be- 

 comes darker, thus bringing about a certain adaptation of the 

 color of the animal to that of its surroundings. This change 

 is effected by means of changes in the pigment cells of the 

 skin in the same manner as in the frog, which will be more 

 fully described later. 



Toads are nocturnal in habit. During the day they lie 

 concealed under stones or in other damp, shady localities, 

 venturing out only toward evening. They hop about like 

 frogs, although with much less agility. On the other hand, 

 they climb with considerable readiness. They feed upon 

 earthworms, snails, and all sorts of insects. The latter are 

 generally caught by suddenly throwing out the tongue and 



1 See Abbott, Am. Nat., Vol. 16, and Hargitt, Am. Nat.,\o\. 22. 



