22 PREVENTIVE AND REMEDIAL WORK AGAINST MOSQUITOES. 



previously referred to, Culex pipiens was found breeding abun- 

 dantly in them, and more than 1,000 such basins were regularly 

 treated with petroleum. It is a matter of common observation in 

 the city of Washington that during the usually dry period of late 

 July, August, and September mosquitoes are rather numerous in the 

 northwest quarter of the city where there are no possible breeding 

 places other than these catch-basins, and it is urged that under such 

 circumstances residents make an effort to have such basins frequently 

 treated with kerosene. 



The suggestion has been made that in cities it may, under certain 

 circumstances, be possible for mosquitoes to breed in water accumu- 

 lating in the troughs of underground-conduit electric railways, but so 

 far as known to the writer no exact affirmative observations have been 

 made. That there is abundant opportunity for water to accumulate 

 in these troughs and that it does so accumulate there can be no 

 doubt. It is true that such water will immediately become very 

 dirty, since dirt of all kinds falls into the slot, and it would also be 

 more or less oily. There remains a chance that mosquitoes may 

 breed in this manner, although Gen. George H. Harries, vice-president 

 of the Washington Railway and Electric Company, of the city of 

 Washington, informs the writer that in his opinion this chance is 

 very slight. 



DETERRENT TREES AND PLANTS. 



There are many references in descriptive literature to certain trees 

 and plants in the neighborhood of which mosquitoes are never found. 

 Notable among these are the eucalyptus trees and the castor-oil 

 plant. Of recent years there have been man} T newspaper notes about 

 other plants and in southern States the chinaberry tree is said to be 

 distasteful. 



EUCALYPTUS. 



The statement has often been made that the planting of eucalyptus 

 trees in malarial regions will drive away malaria. This idea had be- 

 come rather firmly grounded before the discovery of the carriage of 

 malaria by mosquitoes. It has been said, for example, that the plant- 

 ing of eucalyptus trees in the Roman Campagna was followed by a 

 notable improvement in the malarial conditions. Eucalyptus oil 

 has been used to keep mosquitoes from biting. Mr. Alvah A. Eaton, 

 of California, wrote to the Bureau of Entomology, in 1893, that in his 

 opinion where the blue gum grows no other remedy against mosquitoes 

 need be sought for. He further stated that, no matter how plentiful 

 mosquitoes may be, a few twigs or leaves laid on the pillow at night 

 will secure immunity. Another correspondent of the Bureau, Mr. 

 W. A. Saunders, wrote from California that he had planted eucalyptus 

 trees about his house nineteen years previously and that they had 



