CHEMOTKOPIC TESTS WITH THE SCBEW-WOBM FLY 31 
On the other hand, in some cases the halogen derivative has almost 
the same repellent value as the parent hydrocarbon. For example: 
Compound Coefficient ! Compound Coefficient 
Crude solvent naphtha (mixture j Para-xylyl chloride 16 
of xylenes) 22 | Chlorinated naphthalene 60 
Naphthalene 65 j Para-dichlorobenzene 82 
Benzene 70 \ 
Bromine has a more marked action in enhancing the repellent 
action of a compound than chlorine. For example: 
Compound Coefficient I Compound Coefficient 
Para-xylyl chloride 16 i Para-xylyl bromide 0.16 
Beta-chloroethyl acetate 3. 6 ; Beta-bromoethyl acetate . 32 
Iodine, is even more powerful than bromine in increasing the repel- 
lent action of compounds. Compare: 
Chloroform, 192; bromoform, 51; iodoform, 6.8. 
The introduction of a nitro (N0 2 ) group into a compound increases 
its repellent action toward screw-worm flies. For example:* 
Compound Coefficient I Compound Coefficient 
Benzene 70 j Nitrobenzene 9. 6 
Para-cymene 46 j Nitrocymene 39 
Naphthalene 65 , Alpha-nitronaphthalene 6.6 
Chloroform 192 | Chloropicrin (nitrochloroform).. 
There is no correspondence in the repellent action of the compounds 
tested and their boiling points. While in the homologous series 
benzene, toluene, and ortho-xylene an increase in boiling point is 
accompanied by an increase in repellent action upon screw-worm 
flies, this is so slight as to be within the limit of error in the results. 
Boiling 
point (° C.) Coefficient 
Benzene 79. 6 70 
Toluene 110. 5 68 
Orthoxylene 144 47 
The following examples show how little relation there is between 
the repellent action and boiling points of compounds : 
(1) Compounds boiling between 142.5° and 161.7° C: Boiling point 
Amyl acetate 142. 5 
Ally! isothiocyanate 150. 7 
Alpha-pinene 154 
Furfural 161. 7 
(2) Compounds boiling between 202° and 220.7° C. : 
Normal-caproic acid 202 
Guaiacol 205. 1 
Citronellal 208 
Camphor 209. 1 
Nitrobenzene 210. 9 
Menthol 212 
Dextro-borneol 213. 5 
Naphthalene 217. 9 
Alpha terpineol 219. 8 
Para-xylyl bromide 220. 7 
Obviously the boiling point would have a relationship to the per- 
sistence of the repellent effect, and materials with a very low boiling 
point would be too volatile to be of practical value as repellents. 
SUMMARY 
In an investigation having as its object the discovery of a repellent 
for blowflies suitable for application upon wounds on domestic 
Coefficient 
75 
16 
58 
5. 
3 
35 
0. 
4 
45 
29 
9. 
6 
98 
13 
65 
12 
0. 
16 
