541 
stones in the bed. These brooks in dry summers have so little water 
that a great many annimals must die. The Simulium get over 
such periods, as the eggs can probably stang a temporary drying 
up. In such. cases the resting time of the egg-stage is 
p ro 1 o n g e d. 
I have always seen a little dampness under the stones in the 
bed of the stream, just where I have found eggs of 5. latipes at 
midsummer tide. Swarms of Imagines may be found several km 
from the water, in which they were hatched. The wind is the most 
important factor in that respect. Copula most frequently take place 
in the air, is also seen in captivity and sometimes on cattle. 
Both sexes form swarms, and any rule can therefore hardly be made. 
The farmers of this neighbourhood have during these last years 
undoubtedly learned better how to take care at the critical moment. 
The actual result of our knowledge is that only one remedy for 
fighting against the Simulium can be recommended, viz. gradually 
acquired immunity, which will be obtained if the cattle come 
out a few hours at a time in April and May, and are exposed to 
smaller attacks, but under inspection. This of course has not only 
reference to older, but also to young animals that have never before 
been exposed to Simulium poisoning. In this way they will soon 
be capable of recistance and not easily be killed by the poisoning. 
(Marts 1925). 
