266 HAROLD H. KING — SOME OBSERVATIONS ON THE BIONOMICS 



when the thirteen survivors, having attained maturity, ceased to feed. Up to 

 this stage, if the sand in which they were living was allowed partially to dry 

 out they became very restless until water was given them again, but hereafter 

 they preferred sand which was only slightly damp. In appearance as w^ell 

 as habits they altered considerably at this stage of their existence. While 

 young and growing they possessed well developed pseudopods and conspicuous 

 dark dorsal markings ; now, however, their pseudopods became small and in 

 colour they appeared uniform yellowish white. 



These thirteen larvae were left undisturbed until April 26th, when one 

 specimen was washed out and found to have pupated — probably within the 

 previous two days, as the eyes had not begun to show the colour which they 

 acquired later. On the following day, by carefully picking over the sand, 

 two more pupse were discovered. Prior to pupating the larvse had made a 

 number of tunnels in the sand, and the pupae were lying in a more or less 

 upright position in the tunnels and near the surface. 



On April 28th the writer left Khartoum, and was absent travelling in the 

 provinces until May .30th, by which date one larva had died and twelve 

 -completed their life cycles, producing eight females and four males. The 

 first had emerged on April 29th or 30th, so the period passed in the pupal 

 stage was probably about six days. 



Immature larva (fig. 1) . — Length 18 mm. Colour yellowish white, with dark 

 markings composed of pubescence. Mandibles dark brown to black, slightly 

 serrated. Anterior margins of the meso- and metathoracic segments dark, 

 except on the venter. A ring of pseudopods, eight in each ring — two dorsal, 

 two lateral, four ventral, — on the anterior third of each abdominal segment 



Fig. 1. — Immature larva of Tabanus ditmniatus, Macq. 



a, lateral view of larva, X 3 ; &, 3rd and 4tli abdominal segments, X 6 ; 

 c, 8tli abdominal segment, X 6. 



except the eighth, well developed (except the dorsal pairs on the first and second 

 segments) and bearing spines or hooks. Spines are also present between 

 the pseudopods on each ring. The rings on the first and second segments 

 edged before and behind with dark pubescence, especially on the dorsum, 

 the pubescence extending between the dorsal and lateral pseudopods, thus 

 enclosing the dorsal pseudopods in a dark ring. On each of the third to the 

 seventh segments inclusive is a patch of dark pubescence between the lateral 



