ANIMALS OF POND AND STREAM 33 



What do you find on the segments of the abdomen ? Examine one with 

 the hand lens and draw what you see. Can you now tell why he assumes 

 his resting position? Probably some of the other water beetles in the 

 aquarium will show a silvery mass on the abdomen. Examine the abdomen 

 of such an animal when taken from the water. Is it still silvery? With 

 what is it covered ? Dip a mullein leaf in water and note its appearance. 

 What is your conclusion ? What device has the mosquito larva to facilitate 

 breathing ? How does the pupa breathe ? Observe the rat-tailed maggot 

 and the water scorpion to see how they have solved the problem of respira- 

 tion under water. (Find out from books if specimens are not to be had.) 

 How has man solved the same problem ? Read up on the life-habits of the 

 diving spider and find out where her eggs are laid and how she supplies her 

 young with air. Did insects probably originate in the water and later 

 come to live on land, or are they essentially land animals, some of which 

 have taken to water ? 



How does the fish breathe ? Fill a small wide-mouthed bottle with 

 carbonic-acid gas from a generator and tie a piece of Bologna sausage skin 

 over the mouth. Drop it into a pint fruit jar one-third full of water. Test 

 i the water at once with litmus paper to see if it is acid. Cover the jar. Test 

 the water again after it has stood for a few hours. What is the application 

 of this experiment to the breathing of a fish or of yourself ? Examine 

 larvae of the following insects and see if you find gills : damsel fly, May fly, 

 and stone fly. 



How does the turtle breathe? the frog? Many of the water snails 

 have a lung cavity, the opening into which may be seen beside the shell. 



Capture of prey and feeding. Watch the dragon-fly larvae in the 

 aquaria. Are they active or sluggish ? Are they easily seen ? How do 

 they secure their food ? Watch the larva of the diving beetle, known as 

 "the water tiger," in an aquarium where there are water sow bugs, benders, 

 j or insect larvae. How does it secure its food ? Put an " electric light bug " 

 j or giant water bug into the aquarium with a couple of small fish or a small 

 frog. Watch to see how he captures the animals. Notice the position in 

 I which the front legs are carried. Observe their structure to see how they 

 ! are particularly adapted to the capture of the prey. Notice the front legs 

 ' of the water boatman, the back swimmer, and the water strider. Pick up 

 the "electric light bug," holding it between the thumb and finger by the 

 edges of the body. Notice the mouth parts are arranged to form a sucking- 

 tube. This is one of the structural peculiarities of the bugs. This type can 

 inflict a painful wound, so be careful in handling the insect. Knowing the 

 ; structure of the mouth parts it will now be easier to understand how 

 the animal makes way with its victim. 



