How to collect and examine the eggs. 



The examination and identification of eggs. In order to obtain 

 eggs of " anopheles" it is necessary to preserve some female mos- 

 quitoes of this kind that have been caught in a native village, until 

 they have deposited their eggs. The best method of keeping 

 mosquitoes alive for this purpose is that recommended by 

 Drs. Stephens and Christophers. A glass "chutney" or " pickle" jar 

 with a wide mouth and a hollow glass stopper is obtained, and after 

 it has been thoroughly cleaned and dried a piece of cardboard is 

 placed in it of such a size that after being forced into the jar it 

 remains firmly fixed (Fig. 7). The stopper is 

 filled nearly to the brim with water, and a thin 

 piece of cork covered with white paper is put to 

 float in it. The mosquitoes that have been caught 

 (both males and females) are transferred from the 

 collecting tubes into the jar, which is then placed 

 upside down upon the stopper in a dark cupboard. 

 If mosquitoes from a village are used, it will usually 

 be found that even after one night some of them 

 will have deposited their eggs. Some of the 

 eggs will almost always be found on the white 

 paper, which can then be removed and placed 

 on the microscope stage, the eggs being examined 

 by reflected light with a half or two-thirds inch objective. 



Great care should, of course, be taken that all the mosquitoes 

 in the jar are of the same species, for, if more than one kind is 

 introduced, it will be impossible to tell to which species the eggs 

 belong. 



The points to which attention should be directed in the examin- 

 ation of an " anopheles" egg are : 



(1) The upper surface. The width of the upper surface 

 should be carefully measured, and it should be especially noted 

 whether the floats almost touch each other on this surface, or 

 whether their inner edges are wide apart. 



(2 ) The floats. The character, size and extent of the floats 

 should be noted, and it should especially be seen whether their 

 inner edges encroach on the upper surface of the egg, or whether 

 the floats are inserted laterally so that their inner edges are wide 

 apart on the dorsum of the egg. 



38] 



Fig. 7. 



(after Stephens and 

 Christophers.) 



