INSECTS, AND THEIR RELATION TO MAN 187 



(b) The Larvce (Wigglers) 



Observations. 1. Put some wigglers in a small bottle of 

 water. What is their shape ? 



2. How do the larvae reach the top of the water ? How 

 reach the bottom ? 



3. Watch the larvae while at the surface. Which end is 

 up? Does the end (respiration tubes) reach through to the 

 air? 



4. What is the position of the larvae while at the surface ? 

 Note. If they lie horizontal to the surface, they are the larvae 

 of the anopheles, the malarial mosquito. 



Conclusions. 1. Explain why the larvae often come to the 

 surface. 



2. How tell the larvae of the malarial mosquito from the 

 ordinary mosquito ? 



Observation. Place some of the larvae in an aquarium with 

 a small native fish, as a sun fish, perch, bass, or shiner. 

 A goldfish will serve. Does the fish eat the larvae? If so, 

 how many does it eat at a meal ? 



Conclusion. Explain one way of ridding a pond of mos- 

 quito larvae. 



(c) Pupa 



Observations. 1. Place a number of larvae in another 

 aquarium. Place a screen over the aquarium, and observe 

 from time to time to see them molt their skins. How does 

 the pupa stage differ from the larva stage ? 



2. Look for empty pupa shells floating in the water. Where 

 do they split open ? What came from them ? 



3. Place a few drops of kerosene on the surface of the 

 water. What happens to the larvae and the pupae? What 

 happens to any winged forms ? 



Conclusions. 1. Explain another way of ridding ponds of 

 mosquito larvae and pupae. 



2. What two ways of destroying larvae and pupae do you 

 now know ? Which one is nature's method ? 



