188 INSECTS, AND THEIR RELATION TO MAN 



3. Which, method do you think is the cheaper and most 

 reliable ? Explain. 



Observations. (Afield trip.) 1. Plot a map of a district, 

 showing all the ponds and streams containing mosquito larvse, 

 also those containing none. 



2. Are mosquito larvse more abundant some places than 

 others ? If so, where ? 



3. Are there fish where no mosquito larvae or pupae are 

 found ? Are there toads or frogs ? Are there other animals ? 



Conclusions. 1. How can you account for the lack of 

 wigglers in some of the ponds or streams ? 



2. How could you free some of the other places of wig- 

 glers ? (Try any experiments you can.) Note. All ponds 

 too filthy or temporary to stock with fish or tadpoles should 

 be drained, or at least covered with a film of kerosene. Use 

 about one ounce of oil to 15 sq. ft. of surface. 



(d) The Adult 



Observations. 1. How many pairs of wings? Of legs? 

 Body regions ? 



2. Find the antennae. Note. The antennas of the males 

 are more bushy than those of the females. 



3. What is the resting position of the adult ? 

 Conclusions. 1. Does the mosquito pass through a meta- 

 morphosis ? Explain. 



2. How tell an adult anopheles or malarial mosquito from 

 the common mosquito or culex ? 



(e) Relation to Man 



Observations. 1. What is malaria ? Why is malaria com- 

 monly associated with low lands, swamps, and stagnant waters ? 



2. Might there be any connection between the number of 

 mosquitoes of any region and the number of cases of malaria? 

 Note. Malaria and yellow fever are now known to be car- 

 ried by mosquitoes. These diseases are caused by small or- 

 ganisms that are in the blood of the infected, or sick. 



