4 
On Coloration in Ticks 
Rhipicephalus 
Creamy pattern on scutum, etc. (x = persists, O = absent) 
dux Donitz 
X 
traces where ornate . 
maculatus Neumann 
X 
at posterior spots, slightly at centre 
pulchellus (Gerstacker) 
X 
at scapular and antero-latcral spots 
Amblyomma 
cajennense Koch 
X 
very slight at light parts 
cohaerens Donitz 
O 
o cooperi Nuttall and Warburton 
O 
o decoratum Koch 
o 
99 99 
X 
very slight at scapulae and marginal spots 
dissimile Koch 
X 
scapular spots 
gemma Donitz 
o 
o hebraeum Koch 
o 
o hirlum Neumann 
o 
marmoreum Koch 
X 
very slight at scapulae 
petersi Karsch 
o 
pomposum Donitz 
X 
middle field, antero-lateral fields, trace 
festoons 
o splendidum Donitz 
o 
testudinarium Koch 
X 
faintly in middle field and basis capituli 
o uncatum Nuttall and Warburton 
X 
where spotted posteriorly 
o variegatum (Fabricius) 
X 
at emargination in middle field and light 
spots 
Aponomma 
decorosum L. Koch 
O 
exornatum Koch 
X 
at scapulae 
o gervaisi (Lucas) 
O or x traces in lateral fields (2 dd) 
o gervaisi var. lucasi Warburton 
O 
in 2 dd 
Hyalomma 
o monstrosum Nuttall and Warburton O 
In addition to the foregoing, I have examined the whole of Dr C. W. Stiles’ caustic- 
treated balsam-mounted Dermacentor material, comprising 58 adults, all of which shows 
the creamy white coloration previously referred to when viewed by reflected light. Stiles’ 
material comprises specimens labelled Dermacentor electus Koch (2^1 $), D. occidentalis 
Marx (1 d 3 $), D. andersoni Stiles (9 d 39 $) and Dermacentor sp. (2 d 1 $)> all of which are 
North American species. 
A. 
The foregoing records show that after caustic potash treatment the creamy 
markings only appear to persist clearly and completely in certain members of 
the genera Dermacentor and Rhipicephalus. Under a high magnification the 
chitin in the region of the creamy markings appears finely granular as if it 
included particulate matter. Dermacentor rhinocerotis, which yields different 
results to the other members of its genus that have been examined, bears dull 
yellowish spots on its scutum in dried specimens, whereas in well-preserved 
alcoholic specimens the spots have a yellow or pale pink metallic lustre; neither 
before or after caustic treatment does the species show a creamy ornamentation. 
The three species of Rhipicephalus examined are the only ones that are at 
present known to be ornate. 
In the remaining genera, when specimens are treated with caustic, all 
