358 RUPERT W. JACK — OBSERVATIONS ON THE 



About the shady borders of this vlei tsetses occur in the greatest numbers in 

 August, and at the bases of the trees, where conditions were favourable, the 

 puparia were found. In every case the puparia were in the soil, either sheltered 

 by a hollow in the trunk of a tree, or, when there was a very sharp incline, 

 as on an " ant-heap," under the exposed roots. Generally the soil was sandy 

 and soft, and often much humiis, dead leaves and vegetable debris were present. 

 One or two puparia were, howevei-, found in hard soil even as deep as one 

 and a-half inches. As it is not to be thought that the larvae could have pene- 

 trated baked " ant-heap " to this depth, one can only conjecture that the cases 

 were very old, and that the larvae entered by a crack or division between the 

 soil and the trunk of the tree, not apparent at the time of digging. The following 

 is a list of the situations where puparia were found at Manzituba : — ■ 



(1) Two large Mubula trees {Parinarium moholaf) within a few yards of the 

 edge of a pool of the river ; six empty puparia were found in August ; gentle 

 slope towards river ; soil sandy clay, moderately soft, leaves and humus present ; 

 the puparia were taken in earth in hollows at the base of the trunks (PI. XVIII, 

 figs. 1,2). 



(2) Clump of Mubula trees on ".ant-heap " on edge of vlei, about 100 yards from 

 the river ; sharp slope on all sides ; soil sandy, much dead leaves and vegetable 

 debris ; 25 empty pupa-cases were taken from hollows about the roots of the 

 trees on the top of the heap and on the sloping sides. Here two pupae were 

 found in hard earth one and a-half inches from the surface ; the top of the earth 

 was covered with leaves and vegetable debris (PI. XVII, fig. 1). 



(3) Mopani tree {Copaifera mopani) on "ant-heap" on edge of vlei, 150 yards 

 from the river, on a sharp slope. There was a collection of humus in the hollow 

 where one empty puparium was found (PI. XIX, fig. 1). 



(4) Clump of Mudlaoza trees (botanical name unknown) on "ant-heap" in vlei, 

 50 yards from the river. One pupa-case in a hollow of the root on the sloping 

 side ; soil very hard on the heap, but a collection of humus at the spot where the 

 case was found (PI. XIX, fig. 2). 



(5) Clump of small unknown trees on the bank of a pool in the river. Three 

 empty puparia were found in the earth on the upper side (away fi-om the water) ; 

 situation close to the trunk, and sheltered (PI. XX, fig. 1). 



(6) Clump of Mubula trees on " ant-heap " in vlei, about 100 yards from the 

 river. Four empty puparia were taken on the sloping side, amongst the roots ; 

 soil sandy, humus and vegetable debris present. 



Negative results were obtained from the soil under bushes, although shaded, 

 sloping, loose, full of humus and covered with leaves. A very considerable 

 amount of time was devoted to digging in such situations. The writer is of 

 the opinion that the instinct of the parent fly is to avoid such places where the 

 pupae would be in danger from the scratching of game birds, etc. Digging at 

 the bases of the mopani trees and the common species of Brachystegia in the 

 unshaded forest away from the river also produced negative results. The soil 

 is almost invariably very hard there, and G. morsitans does not haunt these parts 

 in the dry weather after the trees have lost their leaves. 



