94 THE EARLY STAGES OF TABANID^ 



This is the first and only attempt to separate the sexes of tabanids 

 in the pupal stage. 



Tahanus higiittatus Wiedemann. — The early stp^^es of this species, 

 which is widely spread throughout Africa, occurring from the Cape 

 to the Egyptian Sudan, have been described by King (1908). 



The eggs, which were obtained in the vicinity of Taufikia, Sudan, 

 in the marshes, are deposited in a rounded mass (Plate 1, Fig. 18) 

 on grass and reeds overhanging a pool. One egg mass that was 

 counted contained about 450 eggs. The entire act of oviposition was 

 not timed, but it lasted well over half an hour. When a female is 

 ovipositing, although usually exceedingly shy, the stem on which she 

 is resting may be plucked and carried away or put into a bottle with- 

 out disturbing her. Having deposited the eggs, she covers the mass 

 with a creamy white secretion which turns black after a short time. 



The egg is spindle-shaped, slightly more pointed at one end than 

 at the other, and white in color. Length 2.5 mm. The eggs under 

 observation hatched in about eight days, but possibly under natural 

 conditions, exposed to the sun, the incubation period would be 

 shorter. On hatching, the larvae fell into the water, swam to the 

 sides, and buried themselves in the mud. 



The larvas can swim only on the surface of the water, and progress 

 either by a telescopic movement or by lashing vigorously from side 

 to side. 



Several methods of rearing them were tried. The majority were 

 placed in a large glass vessel containing mud, living grass, and water. 

 Some were put into jars containing only water, others in dishes con- 

 taining moist sand, others again in vessels containing sand and 

 water so arranged that there was a pool at one end of the vessel and 

 moist sand at the other. 



The larvas in the vessel containing mud, grass, and water did well, 

 but many were devoured by predacious insects — e.g., dragon-fly 

 larvae — introduced by accident in the mud and water, and others 

 perished owing to the grass dying and fouling the water during 

 transit. Eventually sand and water in Petri dishes were found to be 

 best, as it could be kept clean and the larvae easily located when 

 wanted. 



