N. CUNLIFFE AND Gr. H. F. NlJTTALL 
343 
adult stages. The basal tarsal hump is absent in the first stage, develops as 
a slight protrusion in the second and gradually assumes a hump-like form in 
the subsequent stages. But in smal] individuals of the second and third 
stages the protrusion is still slight, and as in the first stage there is no trace 
of the distal hump. In normal individuals however, the latter hump is repre¬ 
sented in the second stage by a scarcely perceptible prominence, in the third 
by a slight protrusion and in the fourth onwards by a definite hump. 
The size of the humps is less in the smaller specimens of these later nymphal 
stages. In the adult all the humps are very marked but the structure of the 
leg is subject to variation in individual ticks. The distal humps are somewhat 
6 
First 
Second 
/ S X ~ 
Third 
from 3rd o 
Fig. 3. Ornithodorus moubata, tarsi of fourth legs, in lateral aspect. (N. C. del.) 
smaller in adults from third nymphs than in adults from succeeding nymphal 
stages and also the humps are less marked in the more feebly developed indi¬ 
viduals. 
The tarsus of the first leg of the immature stages shows protrusions occu¬ 
pying the positions of the humps on the first tarsus of the adult. This is the 
case even in the first two stages, as shown in the sketches included in Fig. 3. 
(c) The Spiracle. Fig. 4. 
In Fig. 4 the outline of the cribriform plate is shown for the following 
stages, namely first to seventh nymph (a) to ( g ); males from third and fifth 
nymphs, ( h ) and (?'); and females from fourth and sixth nymphs, (j) and (k). 
Parasitology xiii 23 
