262 
BULLETIN OF THE BUREAU OF FISHERIES. 
use the beetles for food. Of course, in making such a transference care must be 
taken that the same species of beetles are not present in the second pond. This will 
almost never happen, however, even when the two ponds are close together and to 
all appearances the conditions are the same. During the summer of 1920 the only 
fishpond at Fairport in which any Cybister larvse were found was pond 5D. Adults 
were found in several adjacent ponds but no larvse. Similarly, Hydrous larvae 
were confined to ponds 3E, 4E, and 14B, and nothing but straggling individuals 
appeared elsewhere. Dytiscus adults were fairly common in ponds 2, 3, 4, and 8, 
in series D, and in 16B, but not a single larva was captured during the entire sum- 
mer in any pond. The larvse of Thermonectes ornaticollis were confined to pond 12B, 
and none were found in any other pond, although the, §dults were common enough. 
In 1921 the large dytiscid larvse described on page-484, which were probably those 
of Acilius serrdsulcatus , were found only in pond 7D; none could be found in ponds 
5, 6, or 8, all of which are very close to pond 7. The buffalofish fry taken out of 
pond 3E (see p. 250) in July, 1918, were carried only a short distance to another pond 
in the same series, but there they were entirely free from attacks of beetle larvse. 
Such a transference of the fish fry, therefore, is the simplest, the most reasonable, 
the quickest and the most effective method of freeing them from the attacks of beetles. 
It must be borne in mind, however, that in draining a pond either for the destruc- 
tion of the obnoxious beetles or for the transference of the fish fry these latter are 
always subject to increased depredation by the beetles during the operation. The 
lowering of the water brings the larvse and fish fry together in a steadily diminishing 
area. The beetles are almost certain to take advantage of this opportunity and 
kill many of the fry; but the danger is only temporary, and as it can not be avoided 
it must be accepted as one of the means necessary to the ultimate deliverance of 
the fish from their enemies. As in all warfare some sacrifice is necessary in order 
to secure final victory. 
6. There is also another method that merits at least some attention, namely, 
the wintering out of a breeding pond. If a pond is drained in the fall and left dry 
through the winter, all the insect larvas it contains, including any beetle larvse 
that might possibly remain, will be destroyed. The adults will migrate elsewhere 
or will be killed, and in the spring the pond will be clean and free from all obnox- 
ious pests. If a pond were persistently infested with any insect enemies of you rig 
fish, it might be advisable to winter it out. The chances of reinfection during 
the following year will thereby be greatly diminished, and in the majority of cases 
it will remain free from the pests for several years. Here again, however, it must 
be remembered that such a procedure gets rid of all the insect fauna, the beneficial 
as well as the harmful. Consequently, there will not be as much fish food the 
following year, and the fry will be compelled to depend upon whatever happens 
to get into the pond unless they are fed artificially. If the latter method be adopted, 
or if the pond be filled with water pumped from a river or lake, there will probably 
be plenty of food for the fry. In such cases the wintering out of a fishpond is 
one of the most effective methods that can be adopted for getting rid of obnoxious 
insects. On the contrary, if the pond be fed from springs, some provision must 
be made for a food supply the following year. 
