BREEDING TECHNIQUE: EGG LAYING 265 



to keep only those females whose ovaries are seen as two white patches 

 at the sides of the abdomen, an indication that the eggs are ready 



to be laid. Perry also points out that when a number 



r r i i j.1. ^.u u 1-11 Breeding technique: 



of females are kept together they are much more likely E . . | avin g in c ap tj. 



to lay their eggs than if they are kept separately. It v ity 



is true, however, that the females of some species 



whose eggs, at the time of capture, do not appear to be mature, will lay 



them if they are fed and kept long enough. 



The mosquitoes should be placed either in large test-tubes or wide- 

 mouthed glass jars with screw tops. The method of using the tubes is 

 as follows : The tube preferably a large one such as is used for cul- 

 tivating bacteria on pieces of potato should be thoroughly cleaned and 

 dried, and a strip of cardboard firmly fixed in it. After the mosquitoes 

 have been placed in it the mouth is covered with a piece of fine-meshed 

 netting ; it is then inverted over some moist filter paper in a jar and 

 placed in a dark cupboard. If the mosquitoes are wild ones an attempt 

 should be made to feed them the second night after capture ; this is 

 carried out by inverting the tube over the forearm. 



The best form of glass jar is the common jam or preserve bottle with 

 a good screw top ; these can be purchased in most places at a small 

 cost. The method of using such a jar was first devised by Christophers, 

 and is as follows : The jar is cleaned and dried, and a strip of cardboard 

 is fixed diagonally across it ; it is then inverted over its own screw top, 

 which should contain a very small quantity of water and several strips of 

 filter paper. The mosquitoes, on being placed in the jar, will rest on the 

 cardboard. They can be fed by placing the open end of the jar on the 

 forearm ; this is accomplished by raising the jar from its lid until a piece 

 of cardboard can be placed across the mouth ; when the jar is in position 

 on the arm the card is withdrawn. In replacing the jar over the lid the 

 cardboard is slipped under its mouth, which is then placed over the lid, and 

 the cardboard gently withdrawn. The tubes and jars should be labelled 

 and placed in a cupboard ; in cold weather they should be kept in an 

 incubator which registers a temperature of about 75 F. The tubes and 

 jars should be examined daily to see if any eggs have been laid on the 

 filter paper ; all dead mosquitoes and soiled filter paper are removed and 

 if necessary fresh water and paper added. It is best to lift the eggs off 

 the filter paper with a moistened brush, and to place them on a fresh 

 piece of moist paper in a dish containing a small quantity of water ; they 

 may, however, be left on the paper in the screw top, care being taken to 

 renew the water. 

 34 



