F 
DESTRUCTION OF FLY LARVZ IN HORSE MANURi. 13 
effect of 99 per cent. Pyridine was used in two open-pile experiments 
in a dilution of 1 to 1,500 (Table IV, Series 48, A and B), and 8 and 
47 per cent of the larve were killed. 
It is impossible satisfactorily to explain the differences in the larvi- 
cidal efficiency of the pyridine in the cage and open-pile experiments 
where the 1 to 500 dilutions were employed. Different samples of 
pyridine were used in these two tests, and as the conditions are very 
different at Arlington and New Orleans the exact larvicidal value of 
the 1 to 500 dilutions is uncertain. As the 1 to 1,500 is the only dilu- 
tion that is practical from a cost point of view and the larvicidal 
effect of this strength was low, this substance is hardly thought to be 
_ worthy of further consideration as a larvicide. The extremely disa- 
greeable odor as well as the toxicity of pyridine makes its use in 
this work objectionable. 
PLANT MATERIAL TESTED. 
In looking for substances of an organic nature it seemed advisable 
to test material from several common plants and weeds, especial 
attention being given to those that are very abundant and therefore 
cheap. 
Dr. Alsberg suggested the use of plants containing saponin, corn 
cockle being named as a waste product containing considerable 
amounts of this compound. Agave, a saponin-containing plant 
erowing abundantly in Texas and Florida, was obtained by Mr. W. D. 
Hunter and was tried in two experiments. Other plant material, 
some of which contains alkaloids, were also included in the investi- 
gation, namely, ‘“blackleaf 40” (an extract of tobacco), larkspur, 
hellebore, ox-eye daisy, pyrethrum, and stramonium. 
Corn cockle—Corn cockle (Agrostemma githago) is present in wheat 
screenings. The screenings used in this work contained about 43 per 
cent of corn cockle, and hemolytic tests! showed the presence of 
considerablesaponin. Thescreenings were ground and then extracted 
with water for 12 hours. Nine cage experiments at Arlington, using 
extracts of the screenings containing from 0.3 of a pound to 5 pounds 
per 10 gallons, were tried, and the highest apparent larvicidal action 
was 49 per cent. ‘These results varied markedly, and in certain cases 
no larvicidal effect was obtained. Many bacteriological and chemical 
analyses showed no change in the number of organisms or the SOTO 
sition of the manure. 
Agave.—The roots of several agave or soapweed plants (Agave 
lecheguilla) were macerated and water extracts prepared. Two and 
one-half pounds of the finely divided roots were extracted for 12 
1 The hemolytic tests were made by Dr. C. S. Smith, of the Bureau of Chemistry. 
