370 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 16 
the screen. Earwigs attracted by the bait would readily enter and 
feed, after which they would seek a place to hide and find a darkened 
glass vial provided for that purpose. The earwigs were collected the 
following morning and kept in quart jars with cheese cloth covers and 
provided with plant food. 
The following proportions of poison materials were used on the basis 
of four pounds of wheat bran: 
Sodium fluoride (technical) 1, 2, 4 and 8 ounces. 
Calcium fluoride (powdered fluorspar) 1, 2, 4 and 8 ounces. 
Arsenious oxide (technical) 1, 2 and 4 ounces. 
Sodium arsenate (technical) 2, 4 and 8 ounces. 
All lots were moistened with a like mixture of molasses and water. 
In Table I are recorded the total number of earwigs captured in each 
test and the number of dead found in the cages each morning following 
the evening during which the traps were baited. Since the baiting 
was done early in the evening, the counts on the first morning are ap¬ 
proximately twelve hours after the poison was taken. On the second 
morning, a day and a half, and so on. Where a blank space occurs in 
the table after previously recorded dead, it means that no count was 
made on that day. 
When these figures have been reduced to percentages and plotted out 
as a curve, a much better idea of the relative killing value of the differ¬ 
ent mixture can be obtained. This is shown in chart I. In order to 
avoid crowding, the series of sodium arsenate and the one lot of calcium 
fluoride in which marked killing resulted are plotted separately with the 
one curve of arsenious oxide dotted in for a basis of comparison. In 
the jars to which the earwigs were confined it was quite noticeable that 
those which had taken calcium fluoride were quite active, ate the leaves 
provided for food and were practically normal. In all other lots the 
insects were sluggish and did no feeding except a very little at first by 
those baited with the lower strengths of arsenious oxide. 
It will be noticed that sodium fluoride at 2 ounces to four pounds of 
bran was approximately equal in speed of killing to arsenious oxide at 
4 ounces, although in the former case one individual living over, caused 
the upper end of the curve to be extended four days. A comparison of 
the curves of sodium fluoride one ounce and arsenious oxide one ounce 
shows that at this dosage the former was much more effective. Cal¬ 
cium fluoride was the least poisonous of the materials used and in all 
proportions except eight ounces to four pounds, had little effect. The 
earwigs lived over ten days with no material decrease in number, while 
at twenty days a considerable proportion had died through over crowd¬ 
ing and my neglect to feed and water them properly. 
