Teacher's Leaflet. 



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(11). Note on the "head" of the 

 pupa two Httle tubes extending up Uke 

 ears. These are the breathing tubes. 

 Note whether 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? The pupa spends a longer time 

 resting at the surface than the larva. 

 How does it act differently from the 

 pupa of other flies and moths and butter- 

 flies? 



(13). How does the mosquito emerge 

 from the pupa skin? Why does kero- 

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



Mosquito pupa. 



Facts for Teachers. — If it were possible to begin this lesson with the little boat- 

 shaped mass of eggs, I should advise it. These egg masses may be found on almost 

 any rain barrel and they look like a lot o tiny cartridges set side by side, point 

 up, and lashed or glued together to make a raft or boat. Like a certain famous 

 soap, they " float," coming up as dry as varnished corks when water is poured 

 upon them. The young mosquito or wriggler breaks through the shell at the 

 lower end of the egg and passes into the water, and it is a most interesting creature 

 to view through a hand lens. The head and the thorax are rather large while the 

 body is tapering and armed with bunches of hairs. At the rear of the body are 

 two tubes very different in shape; one is long, straight and unadorned, and this is 

 the breathing tube through which air passes to the tracheae of the body. This 

 tube has a star-shaped valve at the tip which can be opened and shut. When 

 it is opened at the surface of the water it keeps the little creature afloat and mean- 

 while it lets air into the body. While it is thus hanging there at an angle of 45 

 degrees to the surface of the water it feeds upon small particles of decaying 

 vegetation; it has a remarkable pair of jaws armed with brushes, which in our 

 common species by moving rapidly set up currents and bring the food to the 

 mouth. This process can be seen plainly with a lens. When disturbed the wriggler 

 shuts the valve and sinks. However, it is not much heavier than the water 

 as I have often seen it rise for some distance without apparent effort ; the 

 other tube at the end of the body is attached to the swimming organs, which 

 consist of four finger-like processes and various bunches of hairs. When swimming 

 it goes tail first, the swimming organs seeming to take hold of the water and pull 

 the creature backward, with a series of spasmodic jerks ; in fact, it seems simply 

 to " throw somersaults," like acrobats. I have often observed wrigglers standing 

 on their heads in the bottom of the jar with their jaws bent under, revolving their 

 brushes briskly, but they never remain very long below the surface as it is nec- 

 essary for them to take in fresh air often. 



The pupa has the head and thoracic segments much enlarged, making it all 

 "head and shoulders" with a quite insignificant body attached. Upon the thorax 



