TYPICAL LESSON PLANS 



139 



to see if those disappear. Place in the aquarium some 

 mosquito larvae ("wrigglers" or "wiggle tails") and 

 watch results. Let the beetle remain a few days without 

 food, then with a pointed stick or pair of forceps hold a 

 small piece of liver in the aquar um near the beetle. It 

 will soon detect it and swim toward it, seizing it with its 

 strong jaws. Note how the front feet are used in helping 

 to hold the bite while the beetle tears it to pieces. 



Problem. — How does the beetle get from the pond to the 

 electric lights ? The answer to this question means a study 

 of wings. This is best done by means of dry specimens 

 with wings spread. Have the children note first on the 

 live specimen the line down the middle of the back where 

 the outer wings meet. With the dry specimen in hand note 

 the shape of the inner wings, and the numerous veins. 

 Are these wings longer or shorter than the outer ones? 

 Why is it that the beetle can keep them entirely concealed 

 when in the water ? One or two specimens should be kept 

 with the outer wings raised to show how the inner wings 

 are folded and tucked away when not in use. 



The Life History. — In scooping up the debris from the 

 bottom of the pond in the spring you will probably capture 

 some of the young cybisters. They do not resemble in 

 any way the mature insects. They are long, slender, seg- 

 mented larvae with six slender legs and hornlike jaws. 

 Place them in an aquarium by themselves and feed them 

 insects, earthworms, or bits of fresh meat. The children 

 will soon discover that the sharp, hornlike jaws are used to 

 seize and kill the prey and suck the juices from their bodies. 

 These larvae are so fierce, and kill so many mosquito 

 larvae and other water insects that they are known as 



