FUMIGATION AGAINST GRAIN WEEVILS 18 
compounds were more toxic than the corresponding chlorine com- 
pounds. From tests on potato-beetle eggs with bromoform, tri- 
methylene bromide, o-bromotoluene, and bromoxylene, Moore and 
Graham (1/7) concluded that the toxicity of organic compounds to 
insect eggs increased with decreasing volatility. Moore (15) also 
tested the action of bromoform, brometone (tribromo tertiary 
butyl alcohol), and ethylene bromide on flies. 
Bertrand and Rosenblatt (2) found benzyl bromide to be more 
toxic than carbon disulphide, but less toxic than monochloroacetone 
to the larve of (Bombyx) Malacosoma neustria L. 
Holt (9) found that it took nine minutes for the vapor of bromo- 
form (0.8 gram per liter) to kill cockroaches (Periplaneta orientalis 
L.), as compared with eight minutes for carbon disulphide at the 
same concentration. 
Organic bromides have the disadvantage of being costly. While 
the bromides are in general more effective than the corresponding 
chlorides, they can not be expected to give an economical fumigant, 
because liquid bromine is usually quoted at a price four to five times 
that of chlorine; furthermore, 35.5 units by weight of chlorine are the 
chemical equivalent of about 80 units by weight of bromine. 
Kthylene bromide and ethyl bromide (Tables 3, 4, 5, 6, 7, 8) are 
the only bromides which seem worth a further trial. 
CHLORIDES 
Trichloroethane, s-tetrachloroethane, propylene dichloride, and a 
mixture of o- and p-dichlorobenzene gave 100 per cent mortality in 
concentrations of 2 per cent or less. Other chlorides showed the 
following order of toxicity: Monochlorobenzene, p-dichlorobenzene, 
tetrachloroethylene, methylene chloride, ethylene chloride, carbon 
tetrachloride, chloroform, acetylene dichloride, trichloroethylene, 
eth ylidene chloride, and isopropy! chloride. 
Tattersfield and Roberts (24) experimented with wireworms. 
Dichloroethylene, trichloroethylene, carbon tetrachloride, chloro- 
form, and tetrachloroethane, in the aliphatic series, and mono- 
chlorobenzene and o-chlorotoluene, in the aromatic series, had a low 
toxicity; 1, 2, 4-trichlorobenzene, monochloroxylene, p-dichloroben- 
zene, and benzotrichloride had a marginal toxicity; o-dichloroben- 
zene and benzal chloride had a moderate toxicity; and benzyl 
chloride had a high toxicity. 
Parker and Long (1/9), using several chlorides against the larve 
of Trogoderma khapra Arrow, at a concentration of 10 ounces per 1,000 
cubic feet and an exposure of 1,000 minutes, obtained a mortality 
of 11 per cent with carbon tetrachloride, 27.7 per cent with tri- 
chloroethylene, 73.3 per cent with tetrachloroethane, and 77.7 per 
cent with pentachloroethane. 
Holt (9), Trillat and Legendre (26), Bertrand and Rosenblatt 
(2), Lefroy (11), McClintock, Hamilton, and Lowe (18), Titschack 
(25), and many other investigators report that chloroform has a low 
toxicity against various insects. 
Altson (1), using the vacuum method commonly employed with 
hydrocyanic acid gas, found tetrachloroethane useless for the fumi- 
ation of beetles in wood. He recommends both o- and p-dichloro- 
enzene as a deterrent to timber beetles. 
Lloyd (12) reports that tetrachloroethane gives good results 
against the white fly in greenhouse fumigation, but is without 
