6．Different animals or pests（有害物） have their special colors？They use their special colors to protect（保护） themselves．
Some birds like eating locusts（蝗虫）．But birds cannot easily catch them．Why？It is because locusts change（改变） their colors together with the change of the colors of crops（庄稼）．When crops are green，locusts look green．But as the harvest time comes，locusts change to the same brown color as crops have．Some other pests with different colors from plants are easily found and eaten by others．So they have to hide themselves for lives and appear only at night．
If you study the animal life，you'll find the main use of coloring is protecting themselves．Bears，lions and other animals move quietly through forests．They cannot be seen by hunters（猎人）．This is because they have the colors much like the tree．
Have you ever noticed （注意）an even stranger act？A kind of fish in the sea can send out a kind of very black liquid（液体） when it faces danger．While the liquid spread over，the enemies（敌人） cannot find it．And it immediately swims away．So it has lived up to now though it isn't strong at all．
Answer the questions according to the passage．
76．Why can't some birds easily catch locusts？It is because locusts change（改变）their colors together with the change of the colors of crops
77．Some pets have different colors from plants．How can they keep out of danger？They have to hide themselves for lives and appear only at night
78．Why can't hunters see bears？Because they have thecolors much like the tree
79．What can the kind of fish sent out when it faces danger？It can send out a kind of very black liquid（液体）when it faces danger
80．Can birds easily find locusts？No，they can't．
