69 



separately upon the water, and has air cells which 

 keep it afloat. In the case of Culex and Taenior- 

 hynchns, hundreds of eggs are cemented together to 

 form rafts, each egg lying perpendicularly, with 

 its larger end pointing downwards. In Culex, the 



Fig. i8. Egg Raft and Eggs of Taeniorhynchus 



egg-rafts are broad and roughly oval in shape 

 (Fig. 17). In Taeniorhynchus, the egg-raft is 

 extraordinarily elongated, resembling, in shape, 

 a racing skiff (Fig. 18). 



The Examination of Ova 



Culex. — Examine the surface of some semi- 

 putrid water for egg-rafts of Culex. Egg-rafts 

 can almost always be found on the surface of 

 water containing macerating leaves, fruit, etc. 

 They are bodies pf a blackish-brown colour, and 

 are readily wafted about by the wind. 



1. Note that the raft is boat-shaped, measur- 

 ing one-fifth to one-third inch in length, and 

 consists of two hundred to four hundred eggs. 



2. Note that the separate ova are smooth 

 elongated bodies, about 07 to o"8 mm. in length. 

 Note that there are no floats or other markings 

 as in the case of Anopheline ova. 



3. Note that one end of the egg is thicker 

 and blunter than the other, and that to the thicker 



