14 BULLETIN 245, U. S. DEPARTMENT OF AGRICULTURE. 
hours in 10 gallons of water. This extract was used in two cage 
experiments and showed a larvicidal action of 82 and 84 per cent. 
The manure was unaffected chemically, and the bacterial count on 
one of these samples was considerably higher than the control counts. 
“ Blackleaf 40.’’—‘ Blackleaf 40,” an extract of tobacco (Nicotiana 
tabacum), containing 40 per cent of nicotine sulphate, is used to a 
considerable extent as an insecticide, and it seemed worth while to 
test its effect on fly larve. It was tried in three cage experiments at 
Arlington, Va., diluted 1 to 50, 1 to 250, and 1 to 500. In none of 
these cases did it show any larvicidal action. 
Larkspur.—Ground seeds of larkspur (Delphinium) were tested, 
using solutions prepared by treating 1 pound of the ground seeds with 
10 gallons of 1 per cent sulphuric acid and allowmg them to extract 
for 12 hours. The extract was applied undiluted, diluted 1 to 5, and 
diluted 1 to 15. The apparent larvicidai effect varied from 57 to 90 
per cent. The bacteria were not affected by the application of the 
undiluted extract, and the only change in the manure noted was a 
decrease of alkalinity due to the acid present in the extract added. 
Stramonium.—A. sulphuric-acid extract of the ground leaves of 
stramonium (Datura stramonium) was prepared by mixing 1 pound 
of the ground dried leaves with 10 gallons of 1 per cent sulphuric 
acid and allowing this to stand for 12 hours. This extract was 
employed undiluted, diluted 1 to 5 and 1 to 15. The larvicidal 
results were not as satisfactory as those obtained above where lark- 
spur extracts were employed. The bacterial count on manure 
treated with the undiluted extract was lowered somewhat, and the 
reaction showed a slight reduction in alkalinity due to the sulphuric 
acid present in the extract applied. 
Hellebore.-—Roots of hellebore (Veratrum album and Veratrum 
viride) were used both in a ground and in a powdered condition. As 
the following results will show, the powdered hellebore proved to be 
the more effective. Both 1 per cent sulphuric acid and water extracts 
of ground hellebore were used in cage experiments at Arlington 
(Table VI, Series 82, 92, 102, and 103), and the results indicate a high 
larvicidal action. 
