12 BULLETIN 1313, U. S. DEPARTMENT OF AGRICULTURE 
to 1,250 cubic centimeters, on roaches (Periplaneta orientalis L.) con- 
fined in a glass-stoppered 1,250-cubic centimeter bottle. Benzene and 
toluene showed the same toxicity. In general, the higher the boiling 
point the longer the time necessary to kill. ‘‘Benzoline”’ (boiling 
point, 60° C.), which killed in 17 minutes, was the most toxic. 
McChntock, Hamilton, and Lowe (13) compared the toxicity of 
the vapors of naphthalene, kerosene, Australene, Oregon fir turpen- 
tine, oil turpentine, Michigan wood turpentine, and oil of Pinus 
palustris on bedbugs, cockroaches, house flies, clothes moths, and mos- 
quitoes in an 800-liter hood. Naphthalene was the most toxic. 
Jewson and Tattersfield (10) found that naphthalene vapor. had 
no apparent effect on mites (Aleurobius farine De G.), even after 
exposure for 16 hours. 
Lloyd (12) found pure naphthalene, free from tarry acids, to be a 
poor fumigant against adult greenhouse white flies (Asterochiton 
vaporariorum Westw.). Ata temperature of 69° to 72° F., 0.5 gram of 
pure naphthalene killed only 3 per cent of the adult white flies con- 
fined in a half-gallon glass-stoppered jar during exposure for an hour. 
Lefroy (11) found that xylene, turpentine, cymene, and pseudocu- 
mene killed 100 per cent, and that eucalyptus oil killed some meal- 
worms dipped in the liquid. 
Russell (22) found toluene more effective than carbon disulphide 
in the partial sterilization of sick soil in which tomatoes were growing. 
Titschack (25) found the vapor of benzene to be very much less | 
effective than carbon disulphide against the eggs, larve, and moths 
of the clothes moth (Tineola biselliella Hum.). Xylene also showed 
a low toxicity, but naphthalene was effective. 
Richardson and Smith (21) found the toxicity toward the black 
aphis (Aphis rumicis L.) to increase from benzene through toluene 
to xylene, but in all cases the tolerance of the host plant, nasturtium, 
was much less than the minimum toxic concentration. Cyclohexane 
was twice as toxic as benzene. 
Tattersfield and Roberts (24) found that anthracene and phenan- 
threne were nontoxic to wireworms; that mesitylene, p-cymene, and 
naphthalene had marginal toxicity; and that n-pentane, n-hexane, 
n-heptane, benzene, toluene, and m- and p-xylene had low toxicity. 
Of the hydrocarbons examined only pseudocumene had moderate 
toxicity. Moore (15) found that the toxicity of petroleum ether, 
benzene, toluene, xylene, gasoline, camphene, Tarphi thrlenes and kero- 
sene toward flies increased with diminishing volatility. 
The low toxicity and ready inflammability of all the hydrocarbons 
tested make this class of organic compounds unpromising in the 
search for a practical fumigant. 
BROMIDES 
The most effective bromide tested during the investigation re- 
ported in this: bulletin was ethylene bromide, which killed 100 per 
cent of the weevils at a concentration of only 0.5 per cent. The 
order of toxicity of the other bromides follows: Bromoform, n-butyl, 
ethyl, allyl, n-propyl, and benzyl bromide, and bromobenzene. 
Bromoform and monobromobenzene were found by Tattersfield 
and Roberts (24) to be moderately toxic to wireworms. Moore (14) 
tested the action on flies of bromobenzene, p-dibromobenzene, o- and 
p-bromotoluene, and bromoxylene. The disubstitution products 
were more toxic than the monosubstitution products, and the bromine 
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