Abstract:
SUMMARY 1: 1. The distribution of H. truncatum (syn. H. transiens) is given in terms of political divisions. 2. The limiting factor to its distribution is seen to be increasing humidity. It is present up to 20 inches per annum. Above this the conditions are marginal and the presence of the tick is dependent on more localized climatic variations and micro-habitats. Where the high rainfall is due to heavy thunderstorms the tick can maintain itself precariously; where the high rainfall is due to a more even distribution in time the tick is unable to exist at the higher rainfall levels. In the Cape Midlands, with a low rainfall, the ticks tend to be absent from mountain farms having snow in winter. 3. Neither dipping nor vegetation types play a limiting role. 4. H. truncatum is shown to occur in all the drier areas throughout Africa, South of the Sahara.
SUMMARY 2: 1. The distribution of H. rufipes is given in terms of political divisions.
2. The limiting factor to its distribution in South Africa is seen to be increasing
humidity. It is present in areas up to 20 to 25 inches per annum. Above this it
can maintain itself in areas with up to 30 inches per annum, where the atmosphere
is dry; but in moist semi-tropical areas at 25 to 30 inches it is either absent or but
precariously established. Also in dry areas it is not able to maintain itself in winter
rainfall areas or in areas with winter snow.
3. Neither dipping nor vegetation types play a limiting role.
4. Data for central Africa are meagre, but its distribution is possibly limited
not only to the lower rainfall regions but possibly also to areas with but one rainy
season per annum.
SUMMARY 3: 1. The distribution of H. glabrum is given in terms of political divisions and is
seen to be confined to a very restricted area of South Africa.
2. The limiting factor is seen to be a humidity / vegetational one. It is tied to
Karoo, which itself is limited by humidity /aridity. Ten to twelve inches rainfall seems
to be the critical range; in a few areas it is present at 15 inches, possibly areas with
long intervening droughts. It can exist in marginal vegetational Karooid areas,
provided these areas have a low a:nnual rainfall; at higher rainfalls it does not
exist in marginal vegetation areas.
3. For record purposes, since we are not quite convinced that H. glabrum is
synonymous with H. turanicum, it has been decided to retain Delpy's name.
