Incubation 



n. . ^ 



122 nEl'OKT OF THE ENTOMOLOGICAL SECTION 



act of ovipositing, and several more seen. No particular Lime of the day seems to be chosen 

 for the act— one was taken ovipositing at 11.40 a.m. and another at 4.40 p.m. — and 



unlike T. huintlataa, Wied., the only other 



^ seroot I have observed ovipositing in the field, 



this tabanid does not tose her natural wariness 



-J,' , J(A*' while engaged in depositing her eggs. In fact, 



' 'At ^'"^ ^^ often more difficult to capture then than 



^1* , M'hen merely sunning herself on a rock. 



The egg-masses (Plate V., fig. 12) vary in 

 '■ size, and no count of the number of eggs 



contained was made, but the average mass 

 -..—.^(yi^Ka!;*?'*'"' ■^'* ' '^ believed to consist of about live hundred. 

 When freshly laid the mass is glistening white 

 and can be seen from a considerable distance, 

 but within a few hours it takes on a mottled 

 grey hue which so closely resembles the 

 colour of the rock that it is not easily detected. 

 ■ While the fly is occupied in laying her eggs, 



7W/<ini«ii'«jiioiovipositiDS(representedbyciossesi. The . uumbers of a tiuy Hymcnopteron assemble 



Ih!.^*^ Vihiek cresses vepnesf-ut fre^hlv l.litl eii^ rna-sses. 



and proceed to add their eggs to the mass, 

 continuing to do so after the fly has gone away. From some twenty egg-masses 

 collected from the rocks about equal numbers of this egg parasite and of the tabanid 

 larva were obtained. Specimens of this Hymenopteron have been sent to the Scientific 

 Secretary of the Entomological Eesearch Committee for determination.' 



One seroot, taken in the act of ovipositing, completed her egg-laying in a collecting 

 box on the evening of April 13. These eggs had hatched by the morning of April 19, 

 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 larvae 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, larvae of various sizes, mostly nearly mature, were taken. 

 Apparently, stones which w'ere not quite or were barely covered with w-ater were chosen by 

 the larvoe in order that they might come up to breathe without losing thair 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 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 cannibalistic habits the number of 

 larviE which could be transported w^as 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 once every two or three days. 



' This proved to bo a new species of Chnhulce, and has been described by Mr. .1. C. Crawford, of 



Washincjtoii, lUKlor tlie nnnic of Trhnoninn /:i'iii/l — Guy -\- K. 'Marshall. 



