December 1945 E-678
United States Department of Agriculture
Agricultural Research Administration
Bureau of Entomology and Plant Quarantine
INSECTICIDAL ACTION CF ORGANIC HALOGEN COMPOUNDS-A COMPARISON OF SELECTED LITERATURE REFERENCES
By C. V. Bowen and H. L. Haller
Division of Insecticide Investigations
Interest in organic compounds containing halogens as insecticides has been stimulated recently by the widespread publicity given to DDT (l-trichloro-2,2-bis(a-chlorophenyl)ethane) (2, 1, 17); by the effectiveness 4 a soil disinfectant in pineapple fields of a mixture containing 1,3-dichloropropylene and 1,2-dichloropropane, the commercial product of which has been called D-D (5); and by 1,2,3,4,5,6-hexachlorocyclohexane, a new British insecticide (20 1). Dichloropropane was first tested as an insecticide 20 years ago Tl3) and was shown to have limited value as a fumigant. DDT is of especial interest because of its high residual toxicity, and D-D because as a byproduct in the chlorination 4f hydrocarbons it is available at a comparatively low cost. 1,2,3,4,5,6-Hexachlorocycloherane, or benzene hexachloride as it is commonly called was discovered to have insecticidal properties in 192 ,nd early in 19143 the gamma isomer was reported to be more toxic to sre
insects than DDT.
D-D, DDT, and benzene hexachloride represent but a small percentage of the total number of halogen-containing compounds that have been tested against a wide variety of insects. Because of the great interest shown in these three products, it appeared worth while to assemble the toxicity data of some other halogen-containing compounds, and to observe the effect of the introduction of one or more halogens into an organic compound on its insecticidal properties. For this purpose publications containing the results of tests with a large number of organic halogen compounds I/ were selected.
Neifert et al. (13) studied the fumigating action of more than 100 volatile organic compounds against grain weevils. Of the 34 organic halogen compounds, 9 were more toxic than carbon disulfide to the rice weevil (Sitophilus oryza (L.)). The most effective bromide tested was ethylene bromide, which at a concentration of only 0.5 percent killed 100 percent of the weevils (S. orza (L.), S. granarius (L.), and Tribolium spp.). The order of toxicity of the other bromides was bromoform; n-butyl, ethyl, allyl, n-propyl, and benzyl bromides; and bromobenzene. Epichlorohydrin, trichloroethane, sym-tetrachloroethane, propylene dichloride, and
/ The names of the chemical compounds are given as they appear in the literature cited.
a mixture of o- and p-dichlorobenzenes at concentrations of 2 percent or less gave 100 percent mortality. m-Dichloromethyl ether had an efficiency comparable to that of carbon disulfide: chloromethyl ether was about half as efficient. Epichlorohydrin, the most toxic substance tested, at a concentration of only 0.09 percent killed 100 percent of S. oryza. Other chlorides showed toxicity in the following order: Monochlorobenzene, 2-dichlorobenzene, tetrachloroethylene, methylene chloride, carbon tetrachloride, chloroform, acetylene dichloride, trichloroethylene, ethylidene chloride, and isopropyl chloride. The bromides in general were more effective than the corresponding chlorides. n-Butyl iodide, the only iodine compound tested, at a concentration of 0.8 percent killed all the weevils.
Roark and Cotton (16) reported further on the toxicity of 303 aliphatic halogen compounds tested as fumigants in the presence of wheat against the rice weevil. The most effective of these compounds, together with the minimum lethal dosages, are listed below.
per liter per liter
tert-Butyl bromide <24 tert-Butyl chloride 34
Epichlorohydrin <24 2-Chloroethyl acetate 47
2-Chloroethyl ether <24 Carbon tetrabromide 60
2-Bromoethyl ethyl etherc27 Isobutyl iodide 64
Allyl bromide < 28 sec-Butyl iodide 64
2-Bromoethyl acetate <30 Isopropyl iodide 68
Methyl bromoacetate < 30 Methyl chloroacetate 73
Ethyl bromoacetate <430 n-Propyl bromide 81
n-Propyl iodide -< 35 Ethyl 1-bromopropionate 84
Allyl iodide < 37 Ethylene dibromide 87
Ethyl iodide < 39 Propylene chlorohydrin 89
Methyl iodide -c46 Ethyl chloroacetate 93
Methylene iodide < 67 n-Butyl iodide 97
The following 19 halogen compounds failed to kill any weevils at the maximum dosage of 0.50 ml. per liter: sym-Tetrabromoethane, 1,2,3-tribromobutane, hexachloroethane, iodoform, trimethylene chlorohydrin, chloromethyl ether, chloroacetic acid, bromoacetyl bromide, chloroacetyl chloride, dichloroacetyl chloride, trichloroacetyl chloride, propionyl chloride, nbutyryl chloride, isovaleryl chloride, n-butyl chloroformate, isoamyl chloroformate, gamnma-bromopropyl acetate, chloral cyanohydrin, and n-butanesulfonyl chloride. From the results presented by Roark and Cotton it is evident that in general the alkyl iodides tested are more toxic than the corresponding bromides and chlorides:, and that the bromides are more toxic
*than the chlorides. Table 1 shows the effect of halogen substitution in some of the compounds tested. Although..in some cases the toxicity was increased by the substitution of a halogen, in a number of others the toxicity was decreased.
Approximately 400 organic compounds were investigated by Fink et
al. (_) to determine their toxicity to Culex mosquito larvae. Of these compounds 96 contained halogens. Of the-65 chlorine compounds 42 showed some toxicity; 18 of the 20 bromine compounds and 12 of the 14 iodine compounds were toxic to some degree. Their results with some of the compounds are shown In table 2 in comparison with those obtained with the parent compound. The introduction of I chlorine or bromine atom in biphenyl resulted in increased toxicity, the substitution of 2 chlorine atoms had the opposite effect, whereas the dibromo and diiodo derivatives were nontoxic. Chlorine substitution decreased the toxicity of dibenzofuran, had no effect on the toxicity of 2-nitrodibenzofuran and 1-phenylazo-2-naphthol, but increased the toxic effect of 4-nitroaniline and Nacetyl-diphenylamine.
Bushland and King (14) more recently have tested 113 organic compounds against mosquito larvae TCulex quinquefasciatus Say). The 24 halogen compounds gave mortalities in 16 hours ranging from 3 percent at a concentration of 100 p.p.m. to 99.5 percent at 1.25 p.p.n.
Table 3 shows the comparative toxicity of related compounds and
results obtained by both groups of investigators on the same compound. No relation between toxicity and the halogen substituent is evident.
European Corn Borer
An investigation by iestel et al. (14) of the toxicity of 122 compounds to the European corn borer taus nubilalis (Ebn.)) included 21 halogen compounds. Five of the 11 chlorine compounds tested were toxic,
2 of the 14 bromine compounds, and all 6 of the iodine compounds. Table 4 shows that in 14 of the compounds tested a halogen substitution resulted in a decrease in toxicity to the corn borer.
Bushland ( ) reports from his tests of 551 organic compounds against screwworm larvae that "one hundred and seventeen compounds containing one or more halogen atoms were tested. Eighteen of these were of outstanding toxicity, but fourteen of these eighteen possessed a nitro group and one was a derivative of quinoline. Two of the compounds were derivatives of diphenyl (the p-chloro and p-bromo). The other halogen compound was betaiodonaphthalene." The p-chlorodiphenyl was more toxic than diphenyl, while the 2-iodo derivative was considerably less toxic. He further states, in regard to the diphenyl derivatives, that "the introduction of a chlorine atom in the pars position of one of the benzene rings enhanced toxicity, but chlorine substituted in the ortho position reduced toxicity. When both benzene rings were substituted with halogen in the para positions, the resultant compounds (14,41'-dibromodiphenyl, 14,1-dichlorodiphenyl) had little or no toxicity." The following 11 compounds were nontoxic at a concentration of 0.67 percent, although the parent compound showed some
toxicity: ,141'-Dibromodiphenyl, 2,4-dibromo-alpha-naphthol, ,'dichloroazoxybenzene, 2,4-dichloro-1-naphthol, 2,6-dichloro-4-nitroaniline, 2-nitro-4-chloroaniline, 4-nitro-2-chloroaniline, 2,14,6-tribromophenol, 2,4,5-trichlorophenol, 2-nitroiodobenzene, and 2,14,6-triiodophenol, 4,4'-Dichlorodiphenyl and 2-dichlorobenzene possessed some toxicity, but the corresponding bromine compounds were nontoxic. A comparison of the toxicity of the biphenyl derivatives to different insects is presented in table 5.
The toxicity of organic compounds to the larvae of the codling moth (Carpocapsa pomonella (L.)) is reported by McAlister and Van Leeuwen (12), and by Siegler et al. (1l8~9).The former rated the compounds according to their efficiency. The chlorine compounds had efficiencies from 0.0 to 98.7 percent, while the bromine compounds rated from 16.4 to 100 percent. No consistency in the toxicity of the halogen derivatives of barbituric acid, diphenylpiperazine, and nitrobenzene is evident from the following list:
Barbituric acid 16.4
Dibromobarbituric acid 65.6
Dichlorobarbituric acid 16.4
Diphenylpiperazine hydrochloride 26.2
No iodine compounds were tested. Siegler, however, reported the percentage of woriy and stung apple plugs, from which, with the check value for his larvae, it may be determined whether a compoundis toxic or nontoxic. Of the 27 chlorine compounds 15 were nontoxic, 5 of the 9 bromine compounds, and 6 of the 7 iodine compounds. Anthraquinone and alpha-furalacetophenone were toxic, but the respective 2-chloro and R-chloro derivatives were nontoxic. Biphenyl was toxic as were also the p-chloro, 2-bromo, and 4,1'dichloro derivatives, but 4,4'-dibromo-, 4,1'-diiodo-, o-iodo-, and 2-iododiphenyl were nontoxic, as shown in table 5.
Siegler et al. (18) also studied the toxicity of the halogenated
benzenes, nitrobenzene, and the three isomeric monohalogenated nitrobensenes, dihalogenated (except difluoro) benzenes, and dinitrobenzenes. The monohalogenated benzenes and the chloronitrobenzenes showed little toxicity to the codling moth larvae. In the bromonitrobenzene series, however, the para derivative was more toxic than the or.tho or the meta compounds. All the
iodonitrobenzenes were toxic, the ortho least and the para most toxic. There was no significant difference in toxicity between the isomeric dihalogenated benzenes. The authors stated that "the data obtained indicate no marked correlation between either the groupings involved or their relative positions, with regard to their toxicity to the codling moth larva."
Tattersfield and Roberts (21), after a study of the influence of
chemical constitution on the toxicity of organic compounds to wireworms (Agriotes opp.), found that the position of the halogen in the aromatic ring was practically without effect, and noted a consistent increase in toxicity on the first chlorine substitution but a slightly greater effect on the second chlorine substitution. The toxicities of related compounds, measured in millionths of a gram-molecule per 1000 Cc. of air found toxic in 1000 minutes at 150 C., are given below. The first figure represents the death point, and the second figure the recovery point.
Carbon tetrachloride 1600
o-Dichlorobenz ene 70-50
p-Dichlorobens ene Marginal
1,2,4 -Trichlorobenzene Marginal
Tests against the webbing clothes moth (Tineola bieselliella (HUM.)) and the furniture carpet beetle (Anthrenus vorax Waterhi.) made by Colman
(6) with 165 organic compounds, )4 of which contained halogens, gave no evidence of a relationship between the toxicity and the halogen substitution. In the following list the lowest ratio between the damage caused by partly grown larvae of the carpet beetle to cloth treated with the test material and to cloth treated with a standard mothproofing agent (sodium fluosilicate) indicates the most toxic compound.
Acetophenone semicarbazone 4.1
g-Chloroacetophenone semicarbazone 1.4
3,4-Dichloroacetophenone semicarbazone 4.2
Benzaldehyde semicarbazone 4.6
o-Chlorobenzaldehyde semicarbazone 10.4
The o-chloro-, 2-chloro-, 2,4-dichloro-, and 2,4,6-tribromo- phenyl esters of -toluenesulfonic acid are rated by Colman as having the same toxicity as the phenyl ester.of 2-toluenesulfonic acid when tested against newly hatched larvae of the webbing clothes moth. With the exception of m-chloro-
acetanilide which gave 100 percent mortality of newly hatched larvae but not of b-weeks-old larvae, no difference was noted in the results obtained with the ortho, meta, and para isomers of the chloro-, bromo-, and iodoacetanilides.
Cupples, Yust, and Hiley ~) reported on ests with more than
300 compounds as possible substitutes for hydrocyanic acid in the fumigation of California red scale (Aonidiella aurantii (Mask.)). Of the 89 organic halogen compounds, 79 showed only slight or no toxicity, 7 moderate toxicity, and 3 decided toxicity. Twenty-four cases of related compounds showing the relative toxicity with change in halogen content are indicated as follows:
n-Octane = 2-Bromooctane
Benzene = R-Dichlorobenzene
Nethylene chloride Chloroform = Carbon tetrachloride
Methyl bromide = Methylene bromide a Bromoform
sym-Dichloroethylene Trichloroethylene > Tetrachloroethyleme
Fluorobenzene = 2-Fluorochlorobenzene
Benzyl chloride = Benzotrichloride
= o-Bromobenzyl chloride
Ether = beta-Bromoethyl ethyl ether
Nitromethane < Chloropierin
Ethyl acetate < Ethyl bromoacetate
= beta-Bromoethyl acetate
n-Propyl acetate = beta-Bromopropyl acetate = gamma-Bromopropyl acetate
Benzyl acetate = Benzyl chloroacetate
Fourteen compounds showed no change in toxicity with increase of
halogen content, three showed a decrease, and six an increase in toxicity.
In toxicity tests of halogenated phenols against goldfish, Gersdorff and Smith (', 10, 11) found that the most pronounced differences between the iodophenols and the chloro- and bromophenols are as follows:
(1) Each iodophenol is more toxic than the corresponding compound containing chlorine or bromine. (2) The ortho and meta compounds have changed places, however, in the order of toxicity so that the latter is the least toxic of the iodophenols. (3) The para compound has a pronouncedly greater toxicity than its least toxic isomer,.it being five times as toxic in the case of the iod6phenols as compared with one and one-half times for the bromo- and chloro- phenols.
The dissimilarity of treatment and the wide variety of compounds
tested in the entomological investigations reported makei the drawing of conclusions difficult. It is apparent, however. that the introduction of halogen into an organic compound may increase, decrease, or have no effect on the insecticidal value, and that the effect on toxicity obtained by the introduction of one of the halogens is no indication of the effect likelyto be obtained by the introduction of a different halogen.
Table l.--Effect of halogen substitution on effectivenes-s ,of compounds
as fumigantt, for wheat againEt the rice weevil
Compound : Minimum lethal dosage 3Weevils killedT
:after 241 hours
M4lirams per liter Percent
Methyl format 39 100
Methyl chioroformate 198 100
Ethyl format 72 100
Ethyl chioroforinate 251 100
Chioroethyl chioroformate )480 100
n-Propyl formate 72 100
n-Propyl chloroformate 542 20
gamra-Chloropropyl chioroformate 60,0 10
Isopropyl formiate 53 100
Isopropyl chloroformate 5140 70
n-Butyl formate 109 100
n-Putyl ch:loroformate 539 0
Isobutyl formats 35 100
Isobutyl chloroformate 520 2
Isoamyl formate 70 100
Isoamyl chioroformate 512 0
Chlo'romethyl ether 532 0
IZ-lichlorometby1 ether 659 100
Diethyl ether 357 10
beta-Bromoethyl ethyl .ether 27 100
alpha,beta-Dichloroethyl ether 188 100
beta, beta-Dichloroethyl ether 214 100
Acetcne 396 100
Chioroacetone 110 100.
Acetic acid 500 0'
Chloroacetid acid 496 0
Chioroacetyl chloride 7)49 0
Dichloroacotyl chloride 790 0
Trichloroacetyl chloride 815 0
Eth~yl acetate 180 100
2-Bromoethyl acetate 30 100
2-Ohioroetbyl acetate )47 100
Ethyl bromoacetate 30 100
Ethyl ch'Loroacetate 93 100
Ethyl dichioroacetate 256 100
Ethyl trichioroacetate 692 100
Ethyl alcohol 790 4
Ethylene chlorohydrin 2)42 100
Ethylene bromohydrin 337 100
n-Pro pyl alcohol 402 60
Propylene chiorobydrin 89 100
Table 2.--Toxicity tests against mosquito larvae, showing parent compound and halogen derivatives
Compound Concentration : Korta3.itF In compared
16 hours with parent
r41-j100 6 5
4 1A'-TXrmb beq 100C
)4,i4'-iiodobipheny'. 100 0 -0
2-Chdorodib6L. ofuran 5
2 -11t r relIb ~z zf Ur a 0
3-CU'I )7r rdbez-u~ 100 0
2-Ni r o 11 ne 100 52+
N-.4c j1 h !r1mine 1013
N. Chloro ac e y~.iphenylamine 100 1-Phan. eze*- 7- nlaphthol 100
)>-(21 -i rpeyao--epto 100 0
Phneol j100 4
o-robnel~ / 20 66
r.-Br orohen etole ~/20 9)4
~.Brouoanisole ~/50 73 0
z-'Bromoas- tole j 092
Hydrasobenzoe 10 92
2-Bromohydi-aobenzene 1/ 1 93
Acenaphthene 20 91I
3-Ghloroacenaphthene ~/20 96
/Deata from Bushland and Xing (4).
Table Toxicity tests of related compounds against mosquito larvae
(Data from Pink et al. (9) unless otherwise stated)
Compound Concentration t Average mortality
After 16 hours ter 40 hours
20, 95 97
grDichlorobenzene 50 99 99
2-Dichlorobenzene 50 gg 96
Z-Dibromobenzene 20 52
1 -Diiodobenzene 40 59
,r-Chloronitrobenzene 40 73
3.4-Dichloronitrobentene 20 95 91
m-Bromonitrobenzone 40 96
o-Bromoziitrobenzene 40 64
L-Bromanitrobenzene, 5 48
m-lodonitrobenzene .20 96
3-Iodonitrobenzene 40 gg
k-lodonitrobenzene 100 0
2-Iodosonitrobenzene "00 5
;>0 it 20
z4itrophenyliodocUer!. -p J 1) 7 36
2-Thiocyanobromobenzen" 1 2 97 96
k-Thiocyanoiodobenzerie 1 2 98 9$3
2 4-Dinitrochlorobenzens 20 96 99
2:4-Dinitrobromobenzone 20 gig 99
Il/ Data from Bushland and King (4).
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(1) ANONMOUS. 19145. New Briti'sh insecticide. Soap and Sanit. Chem.
(2) ANNAJ P. N., and Bureau Staff. 1944. Tests conducted by the
Bureau of Entomology and Plant Quarantine to appraise the
usefulness of DDT as an insecticide. Jour. Econ. Ent.
(51 Scientific Notes) 37: 125-159.
(3) BUSELAND, R. C. 1940. Toxicity of some organic compounds to young
screwworms. Jour. Econ. Ent. 33: 669-676.
(4) --- and KING, W. Y. 1943. Laboratory tests with organic
compounds as larvicides for Culex quinquefasciatus Say.
U. S. Bur. Ent. and Plant Quar. E-585, 15 pp. [Processed.]
(5) CARTER, W. 194 A promising new soil amendment and disinfectant.
Science 97: 383-384.
(6) oOLMAN, W. 19143. Tests of chemical compounds against fabric
insects. U. S. Bur. Ent. and Plant Qar. E-592, 12 pp.
(7) CUPPLS, H. L., TUST, H. R., and HILEY, J. 1936. Tests of possible
substitutes for hydrocyanic acid in fumigation of -California
red scale. Jour. Econ. Ent. 29: 611-618.
(8) TIN, D. ., SMITH, L. E., VIVIAN, D. L., and CLABON, H. V. 1938.
Toxicity tests with synthetic organic compounds against
culicine mosquito larvae. U. S. Bur. Ent. and Plant Qiar.
3-425, 34 pp. [Processed.]
(9) GERSDOM, W. A., add SMITH, L. 3. 1940. Effect of introduction
of the halogens into the phenol molecule on toxicity to goldfish. I. Monochlorophenols. Amer. Jour. Pharm. 112: 197-204.
(10) --- and SMITHE, L. E. 1940. Effect of introduction of the halogens
into the phenol molecule on toxicity to goldfish. II. Monobromophenols. Amer. Jour. Pharm. 112: 316-322.
(11) ---, and SMITH, L. E. 1940. Effect of introduction of the halogens
into the phenol molecule on toxicity to goldfish. III. Monotodophenols. Amer. Jour. Pharm. 112: 389-394.
(12) McALISTRR, L. C., and VAN LIWW, E. R. 1930. Laboratory tests of
miscellaneous chemicals against the codling moth. Jour.
Ioon. Ent. 23: 907-922.
(13) NBITERT, I. ., COO, F. C., ROAE, R. C., TONKIN, V. H., BACK,
E. A., and COTTON, R. T. 1925. Fumigation against grain
weevils with various volatile organic compounds. U. S. ,Dept.
Agr. Dept. Bul. 1313, 140 pp.
UNIVERSITY OF FLORIDA
IIIIII l l\11\ 11\ 11111111111111111111 I N 1111111111111I 1
14 3 1262 092387306
(14) QUESTEL, D. D., GERTLER, S. I., -SMITH, L. Z., and VIVIAN, D. L.
1941. Laboratory and field tests of toxicity of some
organic compounds to European corn borer. U. S. Bur. Ent.
and Plant Quar. 3-557, 17 pp. LProcessed.]
(15) ROARE, R. C. 1944. A list of publications on 2 2-bis(parachlorophenyl)-1,1,1-trichloroethane (called DDTS from 1874 to
April 30, 1944, inclusive. U. S. Bur. Ent. and Plant Qpar.
(Unnumbered), 12 pp. [Processed.]
(16) -----------, and COTTON, R. T. 1930. Test of various aliphatic
compounds as fumigants. U. S. Dept. Agr. Tech. Bul. 162,
(17) ---------........... and McINDO0, N. E. 1944. A digest of the literature
on DDT through April 30, 1944. U. S. Bur. Ent. and Plant
Qpar. E-631, 53 pp. [Processed.]
(18) SIEGLER, E. H., MUNGER, F., and SMITH, L. 3. 1939. Toxicity to
the codling moth larva of derivatives of benzene containing
halogen and nitro groups. Jour. Econ. tnt. 32: 129-131.
(19) -------, MUNGER, F., and SMITH, L. E. 1939. Toxicity of certain
organic insecticides to codling moth larvae in laboratory
tests. U. S. Dept. Agr. Cir. 523, 10 pp.
(20) SLADE, R. A. 1945. A new British insecticide. Chem. Trade Jour.
and Chem. Engine. 116: 2"9-281.
(21) TATTESSFIELD, F., and ROBERTS, A. W. R. 1920. The influence of
chemical constitution on the toxicity of organic compounds
to wireworms. Jour. Agr. Sci. 10: 199-232.
(22) WIESMANN, R. 19)43. Eine neue Methode der Bek&mpfung der Fliegenplagen
in Stallen. Anz. f. Sch&dlingsk.19(1): 5-8. (A translation by Carlo Zeimet was printed under the title "Fly Control in
Stables" in Soap and Sanit. Chem. 19(12): 117, 119, 141, 143.