ANIMAL BEHAVIOR — WALKER 287 



in colonies, each pair building its own nest. But the nests are con- 

 structed close together and are so interwoven that they form a single 

 mass sometimes as much as 8 or 10 feet in diameter to which each 

 pair of birds has its own separate entrance. 



The tailor birds {Sutoria and Orthotomus) sew up the leaves of 

 trees to make cone-shaped enclosures in which to build their nests. 



Variations in the structure of birds' nests could be discussed in far 

 greater detail than is here possible. Every species has its special 

 type of architecture. And then within each species there are in- 

 dividual peculiarities of construction, for individual birds have their 

 own traits and preferences in nest building. 



Horned lizards {Phrynosoraa) ^ frequently though misleadingly 

 called horned "toads," inhabit the western United States and range 

 southward into Mexico and Central America. They live on the hot 

 sands and are very sensitive to any drop in temperature. As soon 

 as the sun goes down they usually burrow into the sand in order 

 to enjoy its warmth through the night. Captive horned lizards fol- 

 low this same habit in the zoo. The cage may show considerable 

 activity during the bright hours of daylight; but with the approach 

 of heavy shadows each animal burrows into the sand, sometimes leav- 

 ing the head in sight, sometimes only the tips of the horns. Some- 

 times they bury themselves completely, leaving no evidence of their 

 presence but a little ridge or disturbed spot in the sand. 



The houses of insects are noteworthy and of great variety. Most 

 people are more or less familiar with the fact that ants live in colonies 

 and have elaborate colonial homes. Wasps and bees are also well 

 known for their homes. The masses of webs that are frequently 

 found in trees are usually the homes of caterpillars. The subterranean 

 burrow made by the digger wasp {Sphecius) in which the female lays 

 her eggs and places cicadas that she has stung into a comatose state, 

 may well be called a home for the young wasps that will hatch from 

 the eggs and will feed on the comatose cicadas. 



Trapdoor spiders and other spiders generally have elaborate and 

 very effective homes. 



Even some fish have homes, for many parent fish construct definite 

 nests in which they deposit their eggs. Conspicuous among these 

 nests are the beautiful little bubble nests made by the fighting fish 

 or bettas {Betta) of the Oriental region. The male blows a nest 

 of bubbles, then careful!}^ takes the eggs in his mouth and blows 

 tliem into the nest where thej^ are constantly tended by him. He 

 constantly restores to the bubble mass any eggs or any young fish 

 that fall out while too small to be ready to go on their own way. 



