KEPOUT OF THE ENTOMOLOGICAIj SECTION 111 



above, the fry \Youlfl be carried into the gudvvals and there do good work, but they 

 would be unable to return to the deep canals and so would eventually be captured by some 

 native who had an eye for the "pot." Only those fish which spent their entire life in 

 the canals would be able to perpetuate their species. 



At the suggestion of Mr. A. L. Butler, Superintendent of Game Preservation, the 

 fish Gyprinodon dispar was, later in the year, made the subject of an experiment. This 

 fish, when mature, attains a length of 8 cm. and exists in Khor Arbat in untold myriads. 

 Khor Arbat is a stream of slightly brackish water running in a gorge in the rocky hills 

 about twenty-two miles N.N.W. of Port Sudan. When in flood I believe it is in places 

 seven or eight feet deep, but at other times it is a shallow stream rippling over and around Cyprinodon 

 stones, and eventually losing itself in the desert. A visit was paid to this Khor early "'*"'' 

 in September, 1909, and one hundred living specimens brought to Khartoum. Considerable 

 difficulty was experienced in persuading them to live in captivity until it was found 

 that while, if placed in jars nearly full of water, most of them died within twelve hours, yet 

 if given only about two inches of water over a layer of sand, they could be transported 

 fairly easily. The jars containing them were carried to Port Sudan by hand and from 

 there to Khartoum by rail. No mosquito larvae were obtainable at Khor Arbat, but a 

 number, offered them on their arrival at Khartoum, were readily taken. This, however, is 

 not conclusive proof that G. dispar feeds on mosquito larvae in its natural state, as the 

 fish had then been without food for two days. As they did not thrive in captivity, 

 advantage was taken of the permission very kindly granted by Mr. A. Maclntyre, Acting 

 Manager of the estate at Zeidab belonging to the Sudan Plantation Syndicate, Ltd., 

 to place them in a gudwal on the Company's Estate. A short length of gudwal — about 

 fifty yards — was utilised for the purpose, and the pipe connecting it with the canal, 

 netted to prevent other fish gaining access. This gudwal was not needed for irrigation 

 purposes so the water was allowed to stagnate, fresh water being occasionally added to 

 prevent it from drying out. Owing to various reasons — leave and duty — I was unable 

 to visit Zeidab again until March, 1910, when I was told by Mr. Maclntyre that the 

 fish had lived in the gudwal until the end of January — that is, for over four months — when, 

 as the water had become very overgrown with weeds and slime, he had transferred 

 them to one of the canals, fearing that though still apparently healthy they would die 

 if left longer in the filthy water. During the four months that they were in the gudwal 

 he had been unable to find any mosquito larvae in it. It is almost certain that mosquitoes 

 laid eggs in this gudwal during that period, for in March there were numbers of the 

 larvae of Pyretophorus costalis and a Gulex sp. in another gudwal containing water not 

 far distant. 



The results of this experiment were so promising that it was decided to make an 

 attempt to establish G. dUpar in some place in or near Khartoum, from whence supplies 

 might be sent to anyone requiring them. H. E. the Governor-General very kindly 

 granted permission for a large reservoir in the Palace gardens to be used for the 

 purpose, and Mr. C. J. Slade, Towm Engineer, Khartoum, and Mr. F. S. Sillitoe, Experiment.s 

 Superintendent of Gardens, rendered invaluable aid to the scheme by having all the ";"^. 

 fish already in the reservoir removed — no small task — and by giving general assistance. 

 This reservoir is some eight feet deep, has brick sides, and is fed from the river by a pump, 

 the water being conveyed from the pump to the i-eservoir by a wooden gutter. This 

 gutter was fitted with a wire net to prevent river fish from finding their way into the 

 reservoir. Early in April over two thousand living fish of various sizes, mostly immature, 

 were brought from Khor Arbat and of these about sixteen hundred were placed in the 



