138 NATURE STUDY AND AGRICULTURE 



Problem. — How does the beetle move? What is the 

 position of the body while the beetle is swimming ? How 

 many legs has it ? Which ones does it use most in swim- 

 ming? Watch carefully to see if the strokes are made 

 with both hind legs at the same time. Do these legs differ 

 from the others in structure ? Look carefully and you will 

 find that these legs are broad and thin and have a fringe of 

 long hairs on them. Watch these hairs while the beetle 

 is swimming to see if they change positions. When the 

 stroke is made the hairs are spread to make the leg more 

 oarlike. As the leg is lifted after the stroke the hairs droop 

 downward close to the leg. The children can see this per- 

 fectly. Watch the beetle dive to the bottom of the glass. 

 Does it go head first? 



Problem. — How does this beetle breathe? When the 

 beetle is resting in the aquarium what position does it 

 take in the water? You will find it hanging head down- 

 ward and with the tip of the abdomen protruded above the 

 surface. If it is suddenly disturbed it dives quickly to the 

 bottom while one or two small bubbles of air may be seen 

 coming from the tip of the wing covers. This gives a clue 

 to its method of breathing. When it is resting with the tip 

 of the body above the surface it lifts its wing covers slightly, 

 air rushes in, and is held by fine hairs on the back. Ar- 

 ranged in rows on each side of the back are breathing pores 

 through which the air passes into the body. The space 

 under the wings holds air enough to last the beetle for some 

 time under the water. 



Problem. — How does the beetle eat, and what does it 

 eat ? Place in the aquarium some small bits of lean meat, 

 fresh liver, or some fish food used for goldfish. Watch 



