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 humus, dead leaves and vegetable debris were present. 
One or two puparia were, however, 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 mobola?) 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 (Pl. X VITI, 
figs. 1, 2). 
(2) Clamp 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 (Pl. X VII, 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 (Pl. 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 from the water) ; 
situation close to the trunk, and sheltered (Pl. 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, ete. 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, 
