266 MEDICAL ENTOMOLOGY 



The eggs of mosquitoes may be collected in the places in which they 

 are laid by searching for them with a good hand lens. Those of the 

 Anophelina will be found lying on any vegetable matter 



at the ed S e of water > either arranged irregularly or in 

 characteristic star-shaped patterns ; their glistening 

 appearance and the presence of floats render them easy of detection. It 

 is often only necessary to collect some of the vegetable matter and to place 

 it in a large tray containing some water, and the larvae will appear in a 

 few days. Small collections of water in tins and pots, in holes in 

 rocks and trees are the kind of places where many Culicines lay their 

 eggs, and it is important to remember that, as in the case of Stegomyia 

 and its allies, the eggs may sink to the bottom of the receptacle or 

 hole. In the case of small tins the water should be first stirred 

 up and then poured into a white enamel tray ; as a rule the eggs 

 are dark objects and can be readily recognized with the naked eye. 

 In this way many eggs which adhere to the sides of the receptacle 

 are washed out. Small collections of water in holes in trees and 

 rocks are best removed by syphoning off the water after stirring it 

 up ; if it is thought that any of the eggs are adhering to the sides 

 of the hole fresh water may be added, and the process repeated 

 until they have all been recovered. The well-known egg rafts of many 

 Culicines are such large objects that they cannot escape detection ; they 

 are best lifted out of the water with a brush. 



When the larvae hatch out of the eggs thus collected they should be 

 transferred to specially constructed breeding trays or tanks. The 

 important points connected with the rearing of mosquito larvae are 

 dealt with below. 



Large numbers of mosquito larvae may be collected by dipping for 

 them at the edges of streams, ponds, tanks and similar places. The 



simplest form of dipper, and one with which large num- 

 Collecting Mosquito i r i i j i 



Larvae s larvae can be captured in a short time, is a 



shallow white basin, of which several sizes may be 

 used. One side of the basin is lowered towards the surface of the water 

 where the larvae are floating, and with a sudden movement its edge is 

 passed under the water, which as it flows in carries the larvae with it. The 

 water containing the larvae is then poured into a large bucket, and the 

 dipping process repeated as often as is desired. Large spoons are also 

 used for collecting larvae, but only a few can be caught with them at 

 each dip. In large pools where there is a quantity of thick vegetation 

 it is often difficult to locate the larvae, for they shelter themselves 



