214 
REPORT ON ECONOMIC ENTOMOLOGY 
Tsetse flies 
The eggs under observation hatched in about eight days, but iiossitily under natural 
conditions, exposed to the sun, the incubation period woidd be shorter. On hatching, the 
larvae fell into the water, swam to the sides and buried themselves in the mud. 
The larvcL* can only swim 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 containing 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 larvie in the vessel containing mud, grass, and water did well, but many were 
devoured by predaceous insects — «.(/. dragon lly 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 was found to be best, as it could 
be kept clean and the larvie easily located when wanted. 
At first they were fed on tiny crustaceans dredged from rain pools, but during 
transit, when these could not be obtainetl, scraps of freshly killed raw meat and congealed 
blood from the bodies of gorged mosquitoes were substituted. After arriving in Khartoum 
their diet consisted of earth-worms, as a plentiful supply of these could always be procured. 
They grew very slowly and at greatly varying rates. Two larvie hatched from one 
egg batch on 11th June measured respectively five weeks later, 4 mm. and 15 mm. Owing 
to their telescopic nature it was exceedingly difficult to measure them accurately, so these 
figures must be taken as merely approximate. 
They did not appear to be cannibalistic in their habits, as several of various sizes 
were reared in the same dish and sometimes kept short of food, but were never seen to 
attack each other. When one died, however, its comrades usually devoured it. 
When not feeding they spent most of their time buried in the sand, with just the 
tips of their respiratory syphons showing. If the sand was allowed to dry they became 
very restless, and would make continual efforts to escape from their jars until water was 
given them again. 
Early in .August, when they were about eight weeks old, they ceased feeding and 
were then transferred to jars containing sand to a depth of 6 cm. They descended to the 
bottom of these jars and were still there when, some six weeks later, I went to England 
on leave. 
I returned to Khartoum on 28th January, and the jars then contained several dead 
adults—all males — a few dead inipiB and larviB and a single live larva. This last perished 
early in February without having reached the pupal stage. The empty pujial cases were 
all sticking up out of the sand, the pupie having evidently worked their way up from 
the bottom of the jars by means of their abdominal spines. In several cases the old 
larval skin had remained attached to the caudal teeth of the pupal case. 
The eggs from which these seroots were bred were obtained in the marshes in the 
vicinity of Taufikia. 
Tsetse Flies 
The distribution in the Sudan of the tsetse Hies (lloxsina palpalis, Bob. Desv., and 
(Uosniva moi’sitans, Westw., has been dealt with by Capt. Ensor, E.A.M.C.' 
‘ See jKffje 93 of tliis Roport. 
