12 
Variation in Tichs 
Nuttall (1913), who for some long time had suspected the true cause 
of this variability, but was forestalled in publication by Aragao, has 
since published some remarkable results which he obtained vdth 
RhipicepJialus appendiculatus raised in his laboratory; and, subsequently, 
Cunliffe (1913 and 1914), working in Nuttall’s laboratory, obtained 
confirmatory results with R. pulchellus, and. experimentally, with 
R. sanguineus. 
In the course of work on ticks, chiefly of the genus Amhlyomma, the 
author has come across numerous examples of variabihty of this nature, 
and as the particular case which forms the subject of this note is an 
instance which has occurred under more or less natural conditions, as 
distinct from observations made on laboratory-raised stock, he ventures 
to believe that the case is sufficiently interesting to be placed on record. 
The tick material under consideration is aU derived from a South 
African estate—Gonubie Park—an experimental stock farm, the 
property of Messrs William Cooper and Nephews, situated on the coast, 
some ten miles east of East London. At the time that it was acquired 
by its present owners (1905), the estate was heavily infested with ticks, 
comprising all the species to be found in that part of Africa. The Bont 
tick {Amhlyomma hehraeum) was a common species, and could be obtained 
in large quantities, and, until April or May, 1906, consignments collected 
on the estate were sent to this laboratory at frequent intervals. 
As a result of the regular practice of dipping the stock running on 
the estate, the ticks began to disappear, and by the following season it 
was with the greatest difficulty that we could obtain supphes from this 
source, which had hitherto proved so fertile. The eradication of the 
ticks proceeded so rapidly, that in 1908 the greater part of the estate 
was practically tick-free, and Mr W. F. Cooper, who sent me specimens 
of Amhlyomma, hehraeum at this time, reported that this species was 
confined to a ravine which ran through a part of the estate. This 
ravine had not been cleared, and the rank vegetation afforded excellent 
cover for many kinds of wild game, especially hares and duiker, and it 
was upon such hosts that the ticks had mainly subsisted for two seasons. 
The correlation diagrams (Figs. 1 and 2) represent measurements of 
the length and breadth of the scutum in two lots of Amhlyomma hehraeum 
males. Lot No. C. 263, comprising 80 individuals, was collected by 
Dr S. Williamson at Gonubie Park, in 1905. The diagram (Fig. 1) 
shows that the length of the scutum ranged from 5-7 mm. to 4-2 mm., 
br63/Citli 
the breadth from 4'9 mm. to 3‘5mm., while the mean , ,, ratio is 
length 
