268 MEDICAL ENTOMOLOGY 



should be placed in some form of breeding tank ; the trays used in the 



case of tabanid larvae (see Chapter 4, Section 2) will be found very 



useful for this purpose. The tray should be filled with 



a layer of sand and mud to a depth of three or four 

 from larvae 



inches, and the mud sloped off to simulate the edge of 

 a pond ; fresh water is then poured into the tray until it is about three- 

 quarters full. Some plants and grass should be dug out with their roots 

 from the edge of a pond and planted in the mud ; not only do they 

 afford excellent shelter for the larvae, but their stems and leaves har- 

 bour animalculae and other forms of animal life suitable for food. 

 The tray should be placed in front of a window or on a verandah with 

 an eastern position, so that it receives direct sunlight for several hours 

 in the morning. It may be necessary to cover the tray with a net in 

 order to prevent stray mosquitoes from laying their eggs in the water ; 

 this is accomplished by fixing stout wires to the sides of the tray, as is 

 described in the case of the breeding of the Tabanidae. If large num- 

 bers of adult mosquitoes are required for feeding experiments, larvae 

 can be added to the tray daily, so that imagines will be available on 

 each successive day. 



In the case of tabanid larvae, at least those of the larger species, little 

 or no attention need be paid to the condition of the water in the tray ; 

 although it may become stale, the larvae do not suffer much in con- 

 sequence. With mosquito larvae, however, it is very different. After 

 the water has been standing for several days a pellicle, consisting of 

 flagellates, amoebae and bacteria, forms on the surface, and below this 

 decomposition takes place. This has a most injurious effect on mosquito 

 larvae, and if it is not attended to they cease to grow and eventually die. 

 It is, therefore, important to aerate the water morning and evening, by 

 forcing air through it ; a fine capillary tube and a rubber bulb, such 

 as that attached to some form of syringe, may be used. Darling recom- 

 mends the well-known Pacquelin cautery apparatus, which is used by 

 attaching the double bulb to a glass tube with a capillary canal ; the air 

 is forced through the glass into the water, which then remains fresh for 

 a long time. 



When the larvae pupate, the pupae should be collected with a 



small spoon and transferred a small jar, which is three-quarters full 



of water. A similar jar, with a piece of cardboard fixed 



Methods of keeping inside it> is i nver ted over the mouth of the first ; both 



and feeding mos- 1111, r i 



quitoes should be kept in a safe place. When the mosquitoes 



ha_teh out they fly into the upper jar and rest. on the 



