FUMIGATION" AGAINST GKAIN WEEVILS 17 



Apparently chlorohydrins have not been tested by other experi- 

 menters with insecticides. 



SULPHUR COMPOUNDS 



Methyl and ethyl thiocyanates and allyl isothiocyanate were more 

 effective than carbon disulphide; methyl and ethyl sulphides and 

 ethyl mercaptan were less effective than carbon disulphide. Butyl 

 mercaptan was as effective as carbon disulphide against S. oryza, but 

 only half as effective against the other species of weevils. 



Mercaptol is so slightly volatile as to be ineffective. Cj T anogen 

 sulphide killed no weevils at a concentration of 0.1 per cent; per- 

 chloromethylmercaptolandp-toluenesulphochloridegavevariablekills. 



Richardson and Smith (21) found that a concentration exceeding 

 5 per cent of carbon disulphide was necessary to kill aphids, whereas a 

 solution containing less than 2 per cent injured the nasturtium plant. 



According to Moore {1 5), molecule for molecule, allyl isothiocyanate 

 is more toxic against house flies than chloropicrin, and carbon disul- 

 phide and ethyl mercaptan are more toxic than their relative vola- 

 tilities would indicate. 



Tattersfield and Roberts {24) found allyl isothiocyanate to be the 

 most toxic to wireworms of all compounds tested by them. The 

 toxicity of carbon disulphide was equal to that of benzene. 



Speyer {23) found ethyl mercaptan to have no effect on red spiders. 

 It also failed to kill adult white flies. 



NTTRILES AND ISONITRELES 



n-Valeronitrile had a toxicity as great as that of carbon disulphide;. 

 acetonitrile was about one-fifth as toxic as carbon disulphide. Pro- 

 pionitrile and phenylisonitrile were ineffective. Phenylacetonitrile 

 was the most toxic of this class of compounds, killing all S. oryza at a 

 concentration of 0.10 per cent. 



Moore (14) found that the toxicity of benzonitrile to house flies com- 

 pared with that of iodobenzene and xylene. 



NITRITES 



n-Butyl nitrite and ispamyl nitrite were about equally toxic. 



Moore {15) found that amyl nitrite had about the same toxicity to 

 flies as gasoline. 



Tattersfield and Roberts {24) found that the toxicity of amyl 

 nitrate to wireworms was low and that the toxicity of amyl nitrite 

 was moderate. 



Speyer (23) found that the grubs of a chironomid fly (Orthocladius) 

 came to the surface of the soil of cucumber pot plants and were killed 

 in a short time when amyl nitrite and amyl nitrate were used. He 

 also found that methyl nitrite had a more permanent effect on red 

 spiders than amyl nitrate and tetrachlorethane, but that it was 

 necessary to use concentrations which hurt the plants. The adults 

 of the white fly were killed by all these vapors. 



NITRO COMPOUNDS 



Nitromethane was the only nitro compound which killed all of the 

 insects ; a concentration of 3.6 per cent was necessary. Nitrobenzene, 

 p-chloronitrobenzene, r/t-dinilrobenzene, and a-nitronaphthalene at 

 saturation concentrations killed none of the weevils. 



Moore (15) found nitrobenzene even more toxic than nicotine to 

 house flies. 



16685°— 25f 3 



