JOURNAL OF ECONOMIC ENTOMOLOGY 
298 
[Vol. 17 
it is impossible to predict the amount of benefit derived from this source of 
biological control. 
Although experimental work is now in progress to determine a good 
chemical control, no adequate control measure has been devised to date 
and further work is necessary before presenting any data upon this 
subject. 
Vice-President S. B. Fracker: The next paper on the program is 
by T. J. Headlee. 
CERTAIN DUSTS AS AGENTS FOR THE PROTECTION OF 
STORED SEEDS FROM INSECT INFESTATION 
By Thomas J. Headlee, Ph.D., Entomologist, N. J. 
Agricultural Experiment Stations 
Abstract 
Common white edible beans are protected from later attack by the common bean 
weevil ( Bruchus obtectus ) when mixed in proper proportions with ground burned lime 
(CaO), hydrated lime Ca (OH) 2 , calcium chloride CaCl 2 , calcium sulfate CaSCh, 
dolomite, Highland Clay, Bond D Clay and Milltown Ball Clay No. 9. The pro¬ 
tection which is afforded by these materials is most marked in the case of Milltown 
Ball Clay No. 9, and seems not to be connected with atmospheric moisture or chemical 
state of the dust materials. The protective ability of these materials appears to be 
correlated with the degree to which they exhibit a colloidal character—the more 
colloidal the more effective, the less collodial the less effective. This physical charac¬ 
ter seems to operate through preventing the larva of the bean weevil from obtaining 
sufficient foothold upon the surface of the bean seed to drill its way into the bean. 
Milltown Ball Clay No. 9, which is the most colloidal of all the dust materials worked 
with, appears to afford protection to wheat and shelled corn from later attack by the 
angoumois grain moth ( Sitotroga cerealella). This clay apparently also has an insect 
reducing power when not in direct contact with the immature stages of the insects 
themselves. This insect infestation reducing power appears both in the case of the 
bean weevil and the angoumois grain moth. 
Dusts as Insecticides 
Chambers pointed out that maize commonly protected from weevils 
by mixing the grain with finely powdered wood ashes. He noted that 
the layer of wood ashes on the outside of the sack alone was effective. 
The editor of the publication, in which Chambers’ article appeared 
stated that a layer of building lime on the floor of the storing place and 
between successive layers of bags gives satisfactory results. 
Metcalf * 2 pointed out that mixing air-slaked lime with cow peas in 
Chambers, F. Rhodesia Agr. Journal No. 3, p. 397-398. 1916. 1. c. p. 398. 
2 Metcalf, Z. P. Journal of Econ, Ent. Vol. 10. p. 74-87, 1917. 
