404 Handbook of Nature-Study 



observations may be made casually and leisurely. While the pupils are 

 studying the wrigglers, the following questions should be placed upon the 

 blackboard, and each pupil should make notes which may finally be given 

 at a lesson period. This is particularly available work for September. 



In studying the adult mosquito, a lens or microscope is necessary. But 

 it is of great importance that the pupils be taught to discriminate between 

 the comparatively harmless species of Culex and the dangerous Anopheles 

 and therefore they should be taught to be observant of the way mosqui- 

 toes rest upon the walls, and whether they have mottled or clear wings. 



The Larva. 



Observations: i. Note if all the wrigglers are of the same gen- 

 eral shape, or if some of them have a very large head; these latter are 

 the pupae and the former are the larvae. We will study the larvae first. 

 Where do they rest when undisturbed? Do they rest head up or down? 

 Is there any part of their body that comes to the surface of the water? 



2. When disturbed what do they do? When they swim, do they go 

 head or tail first? When they float do they go upward or downward? 



3. Observe one resting at the top. At what angle does it hold itself 

 to the surface of the water? Observe its head. Can you see the jaw 

 brushes revolving rapidly? What is the purpose of this? Describe its 

 eyes. Can you see its antennas? 



4. Note the two peculiar tubes at the end of the body and see if you 

 can make out their use. 



5. Note especially the tube that is thrust up to the surface of the 

 water when the creatures are resting. Can you see how the opening of 

 this tube helps to keep the wriggler afloat? What do you think is the 

 purpose of this tube ? Why does it not become filled with water when the 

 wriggler is swimming ? Can you see the two air vessels, or trachae, extend- 

 ing from this tube along the back the whole length of the body? 



6. Note the peculiarities of the other tube at the rear end of the body. 

 Do you think the little finger-like projections are an aid in swimming? 

 How many are there? 



7. Can you see the long hairs along the side of the body? 



8. Does the mosquito rest at the bottom of the bottle or aquarium? 



The Pupa. 



9. What is the most noticeable difference in appearance between 

 the larva and pupa? 



10. When the pupa rests at the surface of the water, is it the same end 

 up as the wriggler? 



1 1 . Note on the "head" of the pupa two little tubes extending up like 

 ears. These are the breathing tubes. Note if these open to the air when 

 the pupa rests at the surface of the water. 



12. Can you see the swimming organs at the rear of the body of the 

 pupa? Does the pupa spend a longer time resting at the surface than the 

 larva. How does it act differently from the pupae of other flies and 

 moths and butterflies ? 



13. How does the mosquito emerge from the pupa skin ? Why does 

 kerosene oil poured on the surface of the water kill mosquitoes? 



