-17- 
Culex hortensis Fie. 
•v 
See Roman and Netien ( 243 ) tinder Anopheles maculipennis 
on page l6. ' 
Culex piniens L. , the northern house mosquito 
See Roman and Netien ( 243 ) under Anopheles maculipennis 
on page 16 . 
According to Gimlet te (ill) in 1923, H. E. Durham in 
England found in 1902 that larvae of Culex pjpjens died in less 
than 16 hours (pupae in less than 24 hour if with solutions of 
1:1,000, 1:2,000, and 1:5,000 of whole root of derris; with 
1:10,000 the larvae -were killed in 20 hours and the pupae in 24 
hours. A solution of 1:1,000 of the extract is enough to make 
the water cloudy. 
Gibson ( 107) in 1928 reported that in an experiment con- 
ducted at Hawkesbury, Ontario, Canada, tfhen the pondered derris 
root was dusted on the surfare of the polluted pools of water 
heavily infested, at the rate of 30 pounds per acre of water 
surface, 97 percent of the larvae were destroyed in 48 hours 
and 100 percent in 72. 
Shepard ( 249 ) in 1931 tested the relative toxicity of 
rotenone and nicotine to mosouito larvae. In thdse experiments 
the rotenone was- first dissolved in 95-percent alcohol. This 
alcoholic stock solution was made at a strength of 0.25 gm. in 
100 cc. It was necessary to warm" the mixture somewhat in a 
water 'bath in order. to dissolve the rotenone entirely. On 
dilution with' distilled water a stable milky suspension resulted. 
Both rotenone and nicotine were tested in duplicate at the same 
concentratinn on the same day. All the tests were made as 
ouickly as possible. The spray mixtures were made fresh -each 
day. Rotenone at 0.01 percent without spreader killed 34.5 
percent of mosouito larvae immersed for l/2 hour in the sus- 
pension, as compared "ith a kill of 10.5 percent obtained with 
nicotine under the same conditions. 
Campbell, ' Sullivan, end Smith (55) in 1933 determined the 
relative toxicity of nicotine, anabasine, and other alkaloids, 
and of rotenone for culicine mosouito larvae, Culex pi'oiens L. 
and C. territans Walk. These tests against mosouito larvae 
showed that rotenone is much more toxi? than nicotine. Although 
Shepard also found th r t rotenone is more toxic than nicotine 
for mosouito larvae, he did not do justice to rotenone, "because 
he compared the two compounds at only one concentration, 0.1 
gm. per liter (1:10,000). As shown by these authors, nicotine 
is hot effective at concentrations slightly below 0.1 gm. r>er 
