6 
On Coloration in Tides 
to be confined to the thinner portions of the exoskeleton. That the character¬ 
istic dark markings correspond to thicker and more darkly chitinised portions 
of the scutum is demonstrable by dissections, caustic-treated, or sectioned 
specimens; this being especially evident for instance in Amblyomma. The 
orange spot on the scutum of A. splendidum offers an exception. 
The optical and chemical study of coloration in ticks deserves further 
investigation. 
DESCRIPTION OF PLATES I AND II. 
All of the specimens were viewed by daylight and magnified about x 12 under a Zeiss binocula 
Dissecting Microscope. 
PLATE I. 
Amblyomma hebraeum Koch. Living unfed <$, 2 months old (reckoned from last eedysis). 
A. hebraeum Koch. Living unfed 2 months old. 
A. gemma Donitz, scutum of living unfed $, about 2 weeks old. 
A. hebraeum Koch, scutum of living <$ after sojourn of 77 days on the host. 
A. gemma Donitz, scutum of living unfed about 2 weeks old. 
PLATE II. 
Fig. 1. Dermacentor venustus Banks, living <$. 
Fig. 2. D. venustus Banks, living 
Fig. 3. D. variabilis (Say), living 
Fig. 4. D. reticulatus niveus Neumann, living <$. 
Fig. 5. D. reticulatus niveus Neumann, living 
Fig. 1. 
Fig. 2. 
Fig. 3. 
Fig. 4. 
Fig. 5. 
