-100- 
Musca domestics L., the housefly 
In a study of the toxioity of poisons applied jointly, the nu- 
merical relations are illustrated by a test on the toxioity to the 
housefly of solutions containing pyrethrin and rotenone. A Mixt- 
ure with a little less than four equitoxic units of pyrethrin to one 
of rotenone agreed closely with the definition, but one in which the 
ingredients were about equally balanced showed a significantly great- 
er toxicity than expected on the hypothesis of independent action, 
indicating the presence of synergism.— Bliss (58) • 
The terms "synergism" and "antagonism" have been used to des- 
cribe modes of action of mixtures in which the toxicities are respec- 
tively greater or less than those predicted from the separate con- 
stituents • This definition is illustrated by an analysis of data 
obtained by Le Pelley and Sullivan in tests on the toxicity of rote- 
none and pyrethrins and mixtures of these poisons to M. domestics , 
in which tests synergistic action was demonstrated.— Finney (186 ). 
In a study on the effect of using reduced dosage and reduced 
time exposure in the Peet-drady test, experiments were carried out 
with two finished sprays, one containing 150 mg./lOO ml. pyrethrins 
(equivalent to 7.5 percent ef pyrethrum 20il conoentrate), and the 
other 55 mg./lOO ml. pyrethrins plus 50 mg./lOO ml. of c. p. rote- 
none, both in a deodorized kerosene base. The reduction of exposure 
from 10 to 5 minutes did not cause any substantial changes in the 
knockdown and kill of houseflies when the standard 12 ml. dosage was 
used. The reduction of exposure time, caused a notioeable decrease 
in knockdown and kill when the 6 ml. dosage was used. The reduction 
of the dosage from 12 ml. to 6 ml. caused a decrease in both knock- 
down and kill. The reduction of exposure time did not appear to have 
any adverse effect upon the accuracy of the results.— Ford (191 ). 
The roots of Tephrosia virginiana used in a study contained 1.2 
percent of rotenone and 6.7 percent of total extractives. Three 
fractions of the noncrystalline portion were prepared, end the 
toxioity of each to the housefly was compared with that of rotenone. 
The neutral-resin fraction whioh oomprised approximately 50 percent 
of the total extractives had considerable toxicity, but the alkali- 
solution portion (9 percent) and the oil (23 percent) were nontoxic. 
The two crystalline compounds which were isolated from the neutral 
resin were nontoxic to the housefly. In recent tests comparing the 
toxicity of smoke from burning derris and burning pyrethrum, derris 
was much more toxic to the housefly while the cockroach v.as more 
susceptible to pyrethrum. Fumigation with rotenone and pyrethrum 
in the form of a smoke or aerosol is discussed, and methods of 
