C. W. Howard 
165 
when the sulphur has ceased to burn and employing a lOYogs-s- On 
this occasion the time of exposure was measured from the moment 
when the sulphur began to burn, and, as sulphur requires about two 
to three hours to burn, the actual exposure to the 10“/o gas was only 
about three hours. This test, however, gave us some useful results upon 
which to base our future investigations. It was impossible to obtain 
a large number of species of ticks, owing partly to the season being 
unfavourable for excessive development of ticks. Large numbers of 
the Blue Ticks (Boophilus decoloratus, part of which were probably 
B. australis), and some Black-pitted (Rhipicephalus sirniis), Bont 
{Amblyomma hehraeum), and Red-legged Ticks {Rhipicephalus evertsi) 
in various stages were secured. 
The ticks from this test were kept for fifteen days during which 
several examinations were made. Many ticks were found alive. In 
each case it was only the engorged females or nymphs which survived 
the effects of the gas. Unengorged females and nymphs or males 
perished in every case even where they were hidden in places which 
would seem almost inaccessible to a gas placed in the hold with so 
little pressure. One apparent exception to this occurred. A male 
Amblyomma hebraeuin survived from among a lot of ticks placed in an open 
glass jar and hidden under a pile of iron bars. The next day, however, 
it died. The gas at 10 “/o and with this short exposure did not seem 
to be able to penetrate very deeply through obstacles nor did it seem 
to be of equal strength in all parts of the hold. It was decided, 
therefore, to try a new test, employing the gas at 15“/o and giving 
an exposure of twelve hour’s. The ticks were prepared in the same 
manner as on the former occasion except that more species were 
employed and more stages of the various species. 
The application of the gas was started on February 14th at 4 p.m. 
and continued until 2 % of gas was in the hold of the ship which was 
used for the experiment. A storm then arose making it necessary for 
the Clayton to disconnect. The hold of the ship was left partly closed 
until the next day at 4 p.m. when the Clayton was once more connected, 
the hold closed and all openings calked, and the gas forced in until 
it reached 15 "/o- It was left for twelve hours, at the expiration of 
which time it was aired for several hours and the ticks were removed. 
They were taken from their wrappings and placed in glass jars. These 
were left until March 7th during which interval several examinations 
were made. I will detail the manner of arranging the ticks with the 
species and stages employed and the results obtained. 
