EUCALYPTUS 413 



ALLEGED DETERRENT TREES AND PLANTS. 

 There are many statements scattered through the literature that there are 

 certain trees and plants in the neighborhood of which mosquitoes are never 

 found. Notable among these are the Eucalyptus trees and the castor bean plant. 

 Of recent years there have been many newspaper notes about other plants, and in 

 the Southern States the ehinaberry tree is said to be repellant. 



EUCALYPTUS. 



The statement has often been made that the planting of Eucalyptus trees in 

 malarial regions will drive away malaria. This idea had become rather firmly 

 grounded before the discovery of the carriage of malaria by mosquitoes. It has 

 been said, for example, that the planting of Eucalyptus trees in the Roman 

 Campagna was followed by a noted 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, Department of Agri- 

 culture, 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. Sanders, 

 wrote from California that he had planted Eucalyptus trees about his house 19 

 years previously and that they had reached a height of 140 feet. According to 

 his statement an irrigating ditch ran through the grove, but there was never a 

 single mosquito larva in the grove, although on both sides of the grove larvae 

 were plentiful. On the other hand. Dr. A. Duges, of Guanajuato, Mexico, wrote 

 the Chief of the Bureau on September 8, 1900 : 



" I have received your very interesting study of the mosquitoes of the United 

 States and thank you greatly for it. At the end of the book you speak of the 

 utility of Eucalyptus for driving away insects. I have had some experience with 

 these trees. The fresh leaves placed upon the pillow will attract mosquitoes. 

 Thinking that the mosquitoes loved this plant I had placed the branches further 

 away but without result. I have burned the leaves in my chamber, and the 

 cursed beasts have resisted the smoke." 



Eucalyptus trees of many species are now grown generally all through Cali- 

 fornia, and the idea that they drive away mosquitoes must be abandoned. Mr. 

 H. J. Quayle, in Bulletin 178 of the California Agricultural Experiment Sta- 

 tion, states that in the Burlingame section, not far from San Francisco, all of the 

 avenues are lined with Eucalyptus trees, and mosquitoes are most numerous 

 where these trees are most abundant. In 1901 he captured a pint cup of mos- 

 quitoes immediately under Eucalyptus trees. Coyote Point is covered with 

 Eucalyptus trees, yet the construction of a hotel on the point was abandoned on 

 account of the abundance of mosquitoes. 



Edmond and Etienne Sergent, in their anti-malarial work in Algeria, had 

 occasion to study the question of Eucalyptus, and published their results, to- 

 gether with the results of their observations and experiments upon certain other 

 plants supposed to be deterrent to mosquitoes, in the Comptes rendus des Seances 

 de la Societe de Biologic, November 14, 1903. With regard to Eucalyptus they 



