xxiir INSECTA : DIPTERA 361 



Distinguish, amongst the larvae captured, those of the Gnat, 

 the Harlequin-fly, and Tanypus. Examine these, if possible, 

 under the microscope. Look for their eggs and pupae. Sketch 

 the different stages of each insect found, and watch their habits 

 and development, making careful notes. 



Amongst the flies that emerge, distinguish the males and females, 

 and sketch them from the side, in their characteristic attitude when 

 at rest. 



2. In any fairly clean stagnant pond, dip with a net for the 

 various stages of Corethra and Ceratopogon ; when found, study 

 them as suggested in paragraph 1. 



3. Search a swift, clear stream for the early stages of the Eiver 

 Sand-fly (Simulium), and study them. Watch for the moment of 

 emergence of the fly from the pupa, and determine how the fly is 

 protected from death by drowning, as it rises from the submerged 

 pupal cocoon to the surface of the water. 



4. When digging in the garden or field, search amongst the bases 

 of the grass stems for Tipula larvae or pupae. Catch adult Tipula 

 specimens, and distinguish between the male and female. Verify 

 all the points mentioned in the text. 



