N. CUNLIFFE 
375 
Owing to the amount of material in Set F being very small, it was 
necessary to utilise the progeny of a sister to the female used in the 
experiment, in order to gain some idea of the normal variation in size. 
The largest and smallest males were selected from a large series of 
Rhipicephalus sanguineus received from Africa, and measured. The 
scuta of the extremes were found to have the following lengths : 
smallest male 1'6 mm., largest male 33 mm. It will be noticed that 
the variation in size equals that between the smallest tick of Set C 
and the largest of Set F, experimental animals. 
Summary of structural details in which the ill-nourished individuals 
differ from the normal individuals. 
Nymphs 1 . (Fig. 2.) Posterior margin of scutum of dwarf nymph 
is rounded, and the scutum is proportionately shorter ; basis capituli is 
shorter. 
Males. The dwarfs are much less chitinised and of a dark straw 
colour. The scutum is smoother, less punctate and shows practically no 
traces of either lateral grooves or dorsal furrows. The palps have no 
dorsal concavity. The basis capituli is shorter and the posterior cornua 
are much reduced, the lateral salience being less pronounced. The anal 
plates are reduced in size, rounded posteriorly, the outer angle of the 
normal form being absent; they do not project beyond the general 
body surface. Fig. 3 ( W) shows a type of anal plate intermediate 
between those of the male individuals figured. The accessory plates 
are absent in these dwarf specimens. The tarsi are unarmed and 
resemble those of the nymph. The extreme variability of the spiracle 
should be noticed. 
In Fig. 3 the extremes are represented by X (large male) and 
Z (small male), whilst Y represents the spiracle of an intermediate form 
from the same group (Set C) as the dwarf male. The spiracle of the 
latter tends to approach that of the nymph. 
Females. Posterior margin of scutum rounded (without angularity 
chai’acteristic of the normal female); cervical grooves and lateral ridges 
greatly reduced. Tarsi unarmed, resembling those of the nymph. 
We have only considered the largest and smallest individuals. They 
are, however, the extreme examples of regularly graduated series, in 
1 The difference in lateral salience of the nymphal basis capituli from that of either 
larva or adult is remarkable, even in the ill-nourished nymphs. 
