27 
thorax and to the hair which covers its legs. This taking of water by the Tabanidee 
continues during the entire warm part of the day; but not infrequently I observed 
that, on some days especially, large multitudes of them came to the pool after 3 or 4 
o’clock in the afternoon, flying to the water, not in swarms, but singly, from all 
directions. 
This habit of the Tabanide appeared to me in many respects very important, 
especially in the matter of destroying these insects. It appeared to me that if the 
surface of the water were covered with a liquid which would wet the lower surface 
of the insect’s body at the moment of its contact with the water the insect would 
stick to the surface of the water and thus perish. With this end in view, I applied 
kerosene, a liquid which, on getting on the body of the Tabanus, spreads, like oil on 
paper, until it covers the whole body, including the spiracles, and thus causes the 
destruction of the insect from suffocation, even in the case when it succeeds in tear- 
ing itself away from the surface of the pool. Kerosene fully justified all the hopes 
which I placed init. By the third day of my experiments the ‘pool of death,” as I 
called it, was covered with large floating islands of the corpses of the Tabanide. 
These islands soon reached the shore, and, on the lowering of the water level by the 
heat, covered thickly the borders of the pool. 
The insects, in attempting to take in water by the proboscis, were at once wetted 
by the kerosene and became stuck, as it were, to the surface of the pool. In their 
efforts to tear themselves away from the oily surface by the aid of their wings, 
they circled with great velocity on the surface and soon perished. In some cases, 
not at all infrequently, they succeeded in flying away, but in ali such cases they 
either let themselves down near by on the leaves of some bushes or they flew farther 
with a peculiar unusual buzz. Their fate, however, was only postponed a few hours. 
They soon perished (sometimes in five to six hours) from suffocation and poisoning, 
so that at different distances from the ‘‘ pool of death” could be found dead or dying 
Tabanidz whose bodies were more or less covered with kerosene. The ‘pool of 
death” not only attracts the Tabanide from the immediate neighborhood, but from 
remote places, especially when there are no other ‘‘pools of death” near by. More- 
over, further experiments and observations showed that the presence of other pools, 
brooks, and creeks does not detract from the importance of the ‘‘ pools of death” for 
this reason, that a Tabanus has only to attempt once to take water from the ‘‘ pool 
of death” to find certain death, and the insect wiil certainly make this attempt, 
owing to the very active life of the Tabanidex, which fly with great power and for 
long stretches of time. Lastly, it must be mentioned that the most of the Tabanidz 
very unwillingly fly to open places much removed from the woods. For instance, I 
rarely saw Tabanide taking water from a river flowing less than half a mile from 
the nearest parts of the woods where these insects swarmed in great numbers; they 
always took water from a stagnant pool near by. 
To the ‘pool of death” came and met their death all the species of Tabanide 
(Tabanus bovinus, montanus, tropicus, luridus, solstitialis, borealis, maculicornis, Chry- 
sopa relictus, and Ch. cecutiens) [flying] at the time and the place of my experiment. 
Only the Hematopota did not take to the water, and therefore cannot be destroyed 
by this means. 
As to the quantity of kerosene required: To a few square arshin (1 square arshin—= 
0.6 square yard) of the surface of the pool half a pound of kerosene was applied; if 
then the first male Tabanidze which attempted to take water got stuck, a like quan- 
tity of kerosene was added on the following morning; on the other hand, if they 
escaped, more kerosene was added immediately. The required quantity of kerosene .- 
is best poured at different places of the pool, so as to facilitate the covering of the 
whole surface with a uniform layer of the oil. It is essential to add every morning» 
fresh quantities of kerosene. 
In the selection of the pools for treatment with kerosene care should be taken to 
select those where the Tabanidz swarm in greatest numbers and which are for one 
reason or another attractive to them. If there are only a few such, it is best to con- 
