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SCIENCE 



[N. S. Vol. XL VI. No. 1186 



insects can live in sucli regions because of tlie 

 baneful effect of the gases, others believe that 

 insects are unusually abundant there, partic- 

 ularly in regions where more or less injury has 

 been done to vegetation under conditions that 

 formerly existed in some of the smelters. Bees 

 are thought to be particularly susceptible to 

 these gases and it is often claimed that their 

 numbers are so reduced in smelter regions as 

 to seriously affect the fruit crops because the 

 flowers are not properly fertilized. There is 

 no basis whatever for any such claims or 

 beliefs. For several years I have spent all 

 or part of each summer in studying the insects 

 in regions where smelters are located and, for 

 purposes of comparison, in similar adjacent 

 regions, and in no instance have I been able 

 to detect any differences in the number of in- 

 sects or in the extent of insect injui-y, due to 

 the presence of smelter gases. 



During the last three years the Department 

 of Agricultural investigations of the American 

 Smelting & Refining Co. has carried on exten- 

 sive series of experiments to test the effect of 

 sulphur dioxide on various kinds of vegeta- 

 tion. As insects are often covered over by the 

 cabinets when they are placed over the plots 

 of grain or other vegetation for fumigating, I 

 have had many opportunities to watch their 

 behavior when subjected to known quantities 

 of sulphur dioxide. 



The cabinets used in these experiments were 

 about six feet square and five feet high and 

 were made of celluloid with a light framework 

 of wood. Through these cabinets a current of 

 air carrying a known quantity of sulphur diox- 

 ide was driven by means of electric fans. 

 Every precaution was taken to see that the 

 concentration of the gas was constant in all 

 parts of the cabinet throughout the experi- 

 ment. The time of fumigation varied from 

 half an hour to two or three hours. In every 

 experiment a check cabinet where conditions 

 were exactly similar, except for the absence 

 of the sulphur dioxide, was used. The follow- 

 ing sets of definite experiments and observa- 

 tions were made in 1916. 



A number of honey bees were placed in a 

 cabinet where SO^ was being introduced, the 



strength being 1 part of SO, to 1 million parts 

 of air. During the half hour that they were 

 submitted to the fumigation the bees behaved 

 in the same way as did other bees placed in 

 the check cabinet where no gas was being in- 

 troduced. 



In another experiment bees, butterflies, 

 grasshoppers and mosquitoes were placed in 

 the cabinet where 5 parts of SO, to 1 million 

 parts of air was being introduced. The ex- 

 periment was continued for one hour during 

 which time the insects behaved in a normal 

 way, some of the grasshoppers feeding during 

 much of the time as contentedly as they would 

 have fed outside of the cabinet. When the 

 cabinet was removed the insects flew or hopped 

 away and none showed any ill effects due to 

 the confinement for one hour in this concen- 

 tration of the gas. 



At another time while fumigating some 

 alfalfa plants with a very high percentage of 

 SO,, 25 parts of the gas to 1 million parts of 

 air, I watched a number of insects that wero 

 on the plants in the cabinet. The alfalfa wee- 

 vils, adults and larvse, went on with their 

 work undisturbed. Flies, mosquitoes, leaf- 

 hoppers, grasshoppers and ladybird beetles, 

 behaved in a perfectly normal way and at the 

 end of the hour over which the experiment ex- 

 tended, it could not be seen that the fumiga- 

 tion had had any effect on them. 



As the concentration of gas in the last ex- 

 periment was several times as high as we should 

 ever find in the field even quite near the 

 smelters, it is safe to say that the sulphur 

 dioxide given off by the smelters has no effect 

 whatever on the insects in that region. 



It is true that SO, generated by burning 

 sulphur in a room or other enclosed spaces is 

 sometimes recommended for killing insects. 

 But this is used at the rate of 2 lbs. of sulphur 

 for every 1,000 cubic ft. of space. At sea level 

 and at 20° 0. or 68° F. this would give a 

 concentration of gas equal to 24,009 parts of 

 gas to one million parts of air. Even at this 

 rate with prolonged fumigations the insects 

 are not always all killed! 



E. W. DOANE 



STANroED Universitt 



