OF TABANUS DITJiiNIATUS AND TABANUS KINGI. 271 



One seroot taken in the act o£ ovipositing completed her egg-laying in a 

 collecting box on the evening of April 13th. These eggs had hatched by 

 the morning of April 19th, the incubation period being therefore 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 larv?e obtained from wet 

 moss. They refused to feed however and all perished ; 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 w^ere taken larvae of various sizes, for 

 the most part nearly mature. Apparently stones which were not quite, or 

 barely, covered with water were chosen by the larvj« in order that they 

 might come up to breathe without losing their hold, and so avoid the danger 

 of being carried away by the current. Usually only a single larva was found 

 under one stone, and in every case 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 endeavour 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 their cannabalistic 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 wdien hungry, but appeared to need food only 

 once every two or three days. The writer left Khartoum on April 28th, 

 and when he returned on May 30th, the majority of these larvse were 

 dead; one, however^ had completed its life cycle and seven were still living. 

 Six of these seven pupated during the next three weeks, but died as pupse. 

 The pupal period is probably about six days, for one which pupated on 

 Maj^ 5th appeared to be mature on May 11th, when it perished. 



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

 Arbat stream, and the fly must have crept up the stone through several 

 inches of running water before gaining the ;iir. 



Although this Tabanid in its adult form closely resembles T. tceniolciy 

 Pal. de Beauv., in its larval stage it differs markedly from that species. The 

 larva is admirably adapted for clinging to stones in rapidly running water, 

 its unusujilly long pseudopods, armed with powerful hooks, being retractile 

 and capable of being used as suckers. None of the other Tabanid larvae 

 which the writer has seen hitherto has possessed an anal proleg. 



Besides the seven specimens mentioned above as hpvving been t^d^en 

 in the act oi ovipositing, two or more were caught sucking blood from 

 camels. No males were seen. 



