320 C. F. M. SWYNNERTON. 



Landolphia swynnertonii ; and the third (specially common in the area investigated ) 

 is often dominated by the Piptadenia, by the shrubs, Craterispermum laurimnn 

 and Dracaena gazensis, and the liana, Landolphia hirhii (cf. PL xiii, fig. 2). 

 It seems to be the most important in relation to G. brevipalpis, though I have 

 also taken this fly in some numbers in the heavier type. 



A river-bank association that is worth mentioning specially owing to its ubiquity 

 is that which consists mainly of tall, clean-stemmed trees of mowana {Adina in icro- 

 cephala) and mubaba (Khaya nyasica) growing on the immediate edge of streams 

 and, so long as the moisture supply remains ample, resisting the action of the fires. 

 Except where it has been associated with lower woody growth, I have not found 

 it to harbour fly. However, it frequently is thus associated. 



Secondary formations — deciduous in varying degrees — present several very 

 clearly defined sub-types varying from savannah to close wooding, and each 

 Bomewhat closely confined to a particular geological formation. With " wooded 

 pasture " of one or other of these sub-types it covers the bulk of the country. 



The local " formations " are as follows : — 



(1). Very highly deciduous types, such as Pterocarpus sericeus (mumbhiiugu), 

 Pterocarpus angolensis (bloodwood or mubvangazi) — the earliest shedder and latest 

 reclother of all (PL x, fig. 1) — Acacia natalitia (ihlofunga), A. caffra (iguwha), 

 Bridelia micrantha (mushungunu) and others. Considerable stretches of country 

 are covered almost exclusively with bush of these species — open or dense, pure 

 or mixed. Fly spreads in during the rains, but I failed completely to find tsetse 

 in wooding purely of this type during the leafless period even in such shade as there 

 was, and as it is quite unlikely that they can exist there then, it follows that such 

 areas are cleared each year for from one or two to many months at a time. The 

 country carrying these more sensitive types of wooding is characterised by good 

 soil and permanent streams, and much of it by high elevation. It is particularly 

 suited to settlement. 



(2). Lowland bush savannah (PL x, fig. 2), comprising many tree species, 

 but with the mupoza (Conibretum near leonense) dominant on the drier parts and 

 the musekesa {Bauhinia reticulata) on those that are wetter in the rains. The 

 bush is mostly sparse and, the fixes being early and the trees and shrubs low, 

 the shade is destroyed at an early date in a normal year. Rare scattered fly, 

 G. nwrsitans and pallidipes, was to be found in this type of country up to the time 

 of burning, that is in 1918 the end of July, but permanent fly was near by in 

 a more suitable type of wooding — Brachystegia, with vleis. I found no trace of 

 the existence of permanent breeding centres in this type of country — ^the basalt. 



(3). Brachystegia wooding, here known as '' tondo-bush " or " itondo " and 

 evidently identical with what Jack calls " gusu." This again contains a variety 

 of trees and shrubs, but different species of Brachystegia dominate, such as B. 

 globiflora, the mutondo (which gives its native name to the type of wooding), and 

 the mutsatsas, B. randii, B. bragaei and B. spicaeformis, the trees of the red spring 

 foliage. Uapaca also — U. hirhiana (munjanje) especially in the highlands, 

 TJ. sansibarica (mutongoro) below — is common and in many places forms 

 pure wooding. Diplorhynchus mossamhicensis (mutowa), with its weeping 



