THE COMMON AND MALARIAL MOSQUITOES 63 



This is the breathing tube. Note beside it a cylindrical 

 segment (the last) of the abdomen, bearing on its free end 

 some long bristles and four flaps. The flaps function as 

 swimming organs and also, to some extent, as respiratory 

 organs. Note the long bristles along the sides of the thorax 

 and abdomen. Are they branched? Note the tracheae 

 leading from the breathing tube and running throughout 

 the length of the body to the head. Are there any side 

 and cross branches from the two main tubes ? 



Make a drawing of the larva showing all these points. 



To furnish food for the wiggle r put some pond scum 

 into the jar. They ought to grow fast enough in a 

 warm room to become plainly visible at the end of two 

 or three days. Watch them carefully in the water. What 

 position do they occupy? Why? Look at the head and 

 note the movements of the two dark bunches of hair noted 

 above. They create currents of water to bring food to 

 the animal. Do the larvse remain at the top of the 

 water all the time? How do they get to the bottom? 

 Watch one come to the surface. Is there any difference 

 between its descent and ascent? Is it lighter or heavier 

 than water? How does the thorax compare in size with 

 the abdomen? 



Make a drawing of a large wiggler. 



Watch the larvae carefully every day and note any changes 

 that may take place in them. At the end of six to fourteen 

 days dark-colored objects ought to appear in the jars, each 

 with a large anterior end and a slender abdomen. These 

 are the pupce to which the larvse have transformed. Are 

 the pupae active ? Look closely and note the two tubes on 

 top of the thorax. These are the breathing tubes. Re- 

 call the position and number of the breathing tubes of the 



