G. H. F. Nuttall 
3 
Dermacentor variabilis Hunter and Hooker, of which the <$ is illustrated in 
Plate II, fig. 3, is likewise an American species. The ornamentation is usually 
more widely distributed upon the scutum than figured. The illustration is 
from a solitary adult that I succeeded in raising in Cambridge from (N. 1824) 
a lot of larvae received in October 1912 from Dr S. Had wen, the ticks being 
the offspring of females found 24. vi. 1912 on a horse at Glenora, Manitoba, 
Canada. 
The larvae were placed on a rabbit on 11. x. 1912, in Cambridge. Only 5 gorged larvae 
_ were collected, 2 abandoned the host after 4 days, 3 after 5, 7 and 9 days respectively, the 
rabbit being kept in a room at 15° C. Metamorphosis from larva to nymph took place in 
11, 11, 12, 13, 13 days respectively at 21° C. The 5 nymphs were placed upon a rabbit 
17-23 days after emergence, the rabbit being kept at 13° C. Only one gorged nymph was 
recovered after 21 days; it was maintained at 24° C., and after 14 days a <$ emerged. This 
$ survived unfed for 57 days at 22° C. 
A fuller account of the biology of D. variabilis has been given by Hadwen 
(i. 1913, Parasitology , v. 234-237). 
II. ON THE EFFECT OF TREATMENT WITH CAUSTIC POTASH UPON THE 
PIGMENTED PARTS OF ORNATE IXODIDAE. 
Whilst examining some specimens of Dermacentor occidentalis that had 
been treated with caustic potash and mounted by me in balsam in 1879,1 was 
struck by the circumstance that the creamy white pattern was clearly visible 
when the transparent specimens were viewed by reflected light, whereas 
specimens of other ornate ticks, similarly prepared, did not show this appear¬ 
ance. After having examined the balsam-mounted material that was available 
in my cabinet, I selected a series of specimens of ornate ticks from my collection 
of alcohol preserved material, treated them all alike with caustic potash, and 
mounted them in balsam. 
The ticks of the new series (5. vi. 1915) were placed in 10 per cent, caustic potash 
solution at ca. 20° C. for 48 hours, then transferred to water for 24 hours, after which they 
were pricked and pressed between layers of filter paper, cleaned, and placed for 2 days 
in acidulated (H 2 S0 4 ) water and passed through graded alcohols and clove oil prior to being 
mounted in balsam. 
The examination of the cleared and mounted specimens of the males of 
different species gave the following results: observations on older material 
(indicated by o in the list) being included: 
Dermacentor 
albipictus (Packard) 
auratus Supino 
o occidentalis Marx 
reticulatus (Fabricius) 
99 99 
o venustus Banks 
rhinocerotis (de Geer) 
Creamy pattern on scutum, etc. ( x = persists, O = absent) 
x at scapulae, basis capituli, palps, legs 
x at scapulae, basis capituli, legs 
x x complete 
x x complete in 1 d 
x at scapulae, legs, basis capituli, palps in 1 $ 
x x complete in 3 dd 
O 
1—2 
