WERNER MARCHAND 117 



hatched by the morning of April 19, the incubation period being there- 

 fore about five days. Under normal conditions, exposed to the sun, 

 it may possibly be less. The larvae from these eggs were allowed to 

 fall from the egg mass into a basin containing water and stones and 

 were provided with portions of earthworms, and tiny coleopterous 

 and dipterous larvae obtained from wet moss. They refused to feed, 

 however, and all died; probably at this stage of their existence they 

 require brackish running water. 



In places the stream at Khor Arbat is very shallow and ripples 

 over and around stones; under these stones larvae of various sizes, 

 mostly nearly mature, were taken. Apparently stones which were 

 not quite or were barely covered with water were chosen by the 

 larvae in order that they might come up to breathe without losing 

 their hold and so be in danger of being carried away by the current. 

 Usually only a single larva was found under one stone, and, in every 

 instance where two or three were together, a mortal combat was 

 taking place. If a larva was placed on one's hand it would at once 

 endeavor to drive its mouth hooks through the skin, and where the 

 skin was thin, it would succeed in inflicting a sharp pricking pain. 

 Owing to these cannibalistic habits the number of larvae which 

 could be transported was restricted to the number of vessels available, 

 so, though nearly two hundred were taken from the stream, only 

 forty-two were brought alive to Khartoum. There they were placed 

 in jars containing coarse sand, brought from Khor Arbat, and water, 

 and fed on medium sized earthworms. They took these willingly 

 when hungry but appeared to need food only every two or three 

 days. King left Khartoum on April 28, Captain W. B. Fry taking 

 care of the larvae during his absence, and on King's return on May 

 30, the majority of these larvae were dead. One, however, had com- 

 pleted its life cycle and seven were still living. Six of these seven pu- 

 pated during the next few weeks but died as pupae. The pupal 

 period is probably about six days, for one which pupated on May 5 

 appeared to be mature on May 11, when it perished. 



One empty pupal case was taken under a stone in the bed of the 

 Khor Arbat stream; the fly must have crept up the stone through 

 several inches of running water before gaining the air. 



