Related to Horton Hospital Malaria Therapy Unit
Description:

‘Most workers when trying to rear Anopheles maculipennis in the laboratory seem to have relied on artificial foods such as dried yeast, hay infusions, dried and crushed insects, piscidin, etc. Adults can be reared in this way, but the results are far from satisfactory. The larval mortality is always very high; the water must be changed almost daily, and the adults which eventually emerge are, as a rule, much smaller than normal for the species. Furthermore, it is my experience that adults reared on yeast and other artificial foods do not readily bite man and animals.’ (233)

 

'During mosquito survey work in England I have observed that when larvae of A. maculipennis are present in lakes and ponds it is along the grassy edges; they are never present in any part of a lake which is devoid of living vegetation. The method of rearing Anopheles maculipennis is based on this simple fact. Unglazed earthenware pans 18-20 in. in diameter are used. Narrow slices of grass sods are cut from a field or hedgerow and put round the inside rim of the pan. A medium sized tuft is placed in the centre and the pan three parts filled with water. Rain-water only is used; in Epsom the tap water is very chalky and quite unsuitable. The rain-water is filtered through muslin to prevent other insect larvae getting in, such as chiromus, culex, etc. No artificial food of any kind is added and usually no attention is required from the time the newly hatched larvae are added until the adults emerge.’ (233)

 

‘It sometimes happens that a scum forms on the surface of the water... Unless this scum is broken up at once most of the young larvae die... If only one or two breeding pans are in use a football is all that is required to aerate the water. A piece of glass tubing is fitted into the mouthpiece of the rubber bladder and a control clip is fixed on the rubber nozzle of the mouthpiece and the air is allowed to bubble out slowly...

While it is important to break up the scum of the breeding pan it is equally important not to continue to aerate the water once the scum has disappeared because the water will become too clear and the larvae will not have sufficient food.’ (233)

 

‘By the above technique a genetically pure strain of the variety atroparvus has been maintained in the insectory for over three years. It has enabled us to study their habits under laboratory conditions and has provided us with large numbers of insects for malaria therapy work during the season of the year when it is almost impossible to collect sufficient numbers in Nature.’ (234)

 

‘During the summer months it is very easy to maintain a large stock... To ensure a constant supply of eggs during the winter months we examine the adults and collect those which show ovary development. Those adults with mature ovaries are separated and each put into a small glass cylinder resting over a Petri dish containing a little water. It is our experience that adults with mature ovaries in large cages do not readily oviposit during

[image: ‘Fig. 2.- A wooden rack which holds eight glass cylinders, each containing one female adult with mature eggs.’]

the winter. By bringing them into very close contact with water they lay eggs readily.’ (234)

 

‘During the winter, although the temperature never falls below 75˚F., most of the females go into a state of semi-hibernation and those which continue to develop eggs do not lay them so readily as in the summer. The difficulty is overcome by isolating each gravid adult and confining it in a small space with a little water.’ (235)

 

‘The continuous breeding of this variety in the laboratory has enabled us to study its bionomics over a long period. We have been able to observe that there is quite a wide variation of the eggs, especially as regards colour... At the same time we have never seen a batch of eggs which would pass for messeae, typicus or labranchiae. This makes one realise how simple the problem of classification of the races of Anopheles maculipennis would be if only the other varieties could be induced to fertilize in the laboratory.’ (234)

 

‘Because egg-laying is prolific during the summer it may be necessary on occasion to skim off some of the eggs from the breeding pans to prevent overcrowding. This, of course, only applies when adults are flying about in the insectory, as is the case at our centre.’ (235)