394 JOURNAL OF ECONOMIC ENTOMOLOGV [Vol. 7 



cane through the center and at each side. Small, broad-leafed weeds 

 from the cane fields were planted here and there around the edges. The 

 flies seemed particularly fond of these plants, resting on the leaves in 

 the sun, or going under them when it rained. The walls of the cage 

 were made of good quality cheese cloth, and the top of mosquito net. 

 The cloth on the sides shut out most of the strong wind on bad days, 

 and the top net gave the flies a chance to get into extreme sunlight 

 early in the morning or on cool days. 



It was seen that the flies invariably sought the sunlight on the cane 

 leaves or net early in the morning, and as the heat increased they grad- 

 ually went further and further into the shade on the stalks, some even 

 going to the moist shaded soil when the sun was too hot. 



The flies are particularly active as the sun begins to warm up the 

 cage, buzzing about near the top or anywhere they can get into direct 

 sunlight. This is the tim.e that they do their mating, hence it is very 

 important that no obstruction shuts off the morning sun. 



We found that a few cocoanut lea,ves tacked on the outside of the 

 <;age, gave an effect of light and shade that was very satisfactory be- 

 fore we got the cane growing inside. One has to use his judgment in 

 this matter, however, and not everdo it. There must be at least as 

 much surface where the sun can enter as is covered by the leaves. 

 Later, as the green leaves developed inside, the cocoanut leaves were 

 gradually removed, only two or three being retained on the top of the 

 cage as a protection from the noonday sun. 



MOISTUBE 



Flies in general require an almost continual water supply. They, 

 like ourselves, can do for long periods without food, but quickly suc- 

 cumb to drought. Hence tlie matter of supplying moisture required 

 careful regulation. After a good growth of cane was developed in the 

 cages the problem was much simplified, for small drops of water are 

 usually given off by the leaves in transpiration. During dry or windy 

 days it was often necessary to spray the leaves several times. For 

 this purpose an ordinary brass garden syringe with very fine holes 

 was used. The soil, too, was kept well miostened so that the plants 

 would thrive. In rainy weather the surplus water was provided for by 

 boring drainage holes through the floor, and covering them with screens. 

 Small pools of water in the cage are always a source of danger, for the 

 flies sooner or later get into them and are destroyed. 



Liberation of Flies in the Field 



During the development of the flies in the cages a careful survey 

 had been made of the various estates in the Nadi district, preparatory 



