206 EIGENMANN— YELLOW FEVER AND FISHES. 



found in the branches of the Rimac near the bank of the river oppo- 

 site the city and probably in all the pools near Lima. I found great 

 quantities in the foul, knee-deep pools and ponds near Puenta Piedra 

 along the railroad between Lima and Ancon, at Chosica, a health 

 resort inland from Lima, and a native caught some very small ones 

 for me at Matucana at an elevation of over 7,000 feet. 



At Piura, in northern Peru, where during the dry season the river 

 had been reduced to a few pools, in which the fishes had become 

 concentrated, I caught them in great numbers. A few miles farther 

 south, in the Jequetepeque River, I got them up as high as Llallan. 

 The only drawback to this species is its tendency to jump out of the 

 barrels in which it is. placed. 



These are not the only fishes that eat mosquito larvse. In the 

 cisterns of Guayaquil the " millions " are used. The " millions " are 

 minute fishes that came originally from Trinidad or Barbados. The 

 males and females are very different from each other and these fishes 

 give birth to living young. They are called " millions " because if you 

 put a pair of them in a pool "there will soon be millions of them." 

 They are very plentiful in Barbados and the absence of yellow fever 

 from Barbados is credited to the " millions," which do not give the 

 mosquitoes a chance. The " millions " have been transplanted far 

 and wide and are usually part of every novice's aquarium specimens. 



In the United States much has been accomplished in eradicating 

 fever mosquitoes with Gambusia, a small fish which eats the larvae 

 of the mosquito. Mr. S. F. Hildebrand, of the U. S. Bureau of 

 Fisheries, has had charge of this work for the United States Govern- 

 ment and has met with very notable success. It seems that there 

 are many fish eradicators of mosquitoes. Different ones are present 

 in different parts of the world. In most places they need some 

 assistance from man to reach the breeding places of the mosquitoes. 

 It is said in Tampico that upon the appearance of a case of yellow 

 fever the Standard Oil Company spent $3,000 per week to keep the 

 waters oiled to suppress the mosquitoes until a small fish living in the 

 very neighborhood of the plant was put to work and saved all of 

 that expense. 



Of all of the fishes, the " liza de agua duke" of Lima, or the 

 " huaijas," as it is called at Guayaquil, offers the greatest usefulness. 



