608 REPORT OF THE COMMISSIONER OF FISHERIES. 
that ever-present cosmopolitan pest, the mosquito. Howard (1901, 
p. 161) emphasizes the importance of fish in this respect and gives an 
instance where carp are said to have been very effective, though he him- 
self doubts whether carp could have been the fish that destroyed the 
larve. He says: 
It was stated a number of years ago in Jnsect Life, that mosquitoes were at one 
time very abundant on the Riviera in South Europe, and that one of the English 
residents found that they bred abundantly in the water tanks, and introduced carp 
into the tanks for the purpose of destroying the larve. It is said that this was done 
with success, but the well-known food-habits of the carp seem to indicate that there 
is something wrong with the story. If top-minnows or sticklebacks had been intro- 
duced, however, the story would have been perfectly credible, and it points'to the 
practical use of fish under many conditions. Some years ago Mr. C. H. Russell of 
Bridgeport, Conn., described a case in which a very high tide broke away a dike and 
flooded the salt meadows of Stratford, a small town on the north side of Long Island 
Sound. The receding tide left two small lakes nearly side by side and of the same 
size. In one lake the tide left a dozen or so small fish, while the other was fishless. 
An examination by Mr. Russell in the summer of 1891, showed that while the fishless 
lake contained tens of thousands of mosquito larvee, that containing the fish had no 
larvee. @ 
From the results of the stomach examinations recorded in the earlier 
pages of this report it does not seem that Howard’s conclusion that 
carp did not destroy the larve in the tanks in question is warranted. 
While it is true that no mosquito larvee were found among the intes- 
tine contents examined in connection with the present investigation, 
this may have been due to their small size; the fact that in some 
cases the food of the fish seems to have consisted almost entirely of 
insect larvee makes it probable that those of the mosquito would be 
taken as well. Since it is reasonable to suppose that there was little 
or no other food in the tanks mentioned in the above quotation, it is all 
the more probable that the carp would there have eaten the mosquito 
larve, and I see no reason to doubt the original statement. It may 
well be that among our native fish there are some species, such as the 
stickleback and top minnow, which are better adapted to this purpose 
than the carp, but the latter is not for this reason a negligible factor. 
Undoubtedly many ponds that annually breed millions of mosquitoes 
need only to have plenty of fish introduced in order to abate the 
nuisance. If carp will do this as well as other fishes, it will serve a 
double purpose, as it can also be used for food. 
Another, and perhaps even greater, benefit to be derived from the 
the waters where they are present free from mosquito larve. About the hacienda at Chichen-Itza, 
Yucatan, there are a number of large tanks which are kept constantly filled with water for the stock 
and for other purposes. In some of these tanks mosquito larvee were very abundant; but in the 
others, into which a few small native fish, locally known as ‘‘mojarras’’ (Heros urophthalmus), had 
been introduced, none were to be found. The same was true of two natural pools in the vicinity 
where these fish lived, while, on the other hand, large numbers of larvee could be found in small 
hollows in the rock and other places where the rain water had been standing for a few days. 
