472 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 17 
ever, the digestive tract is dissected from the insect, the cells die and so 
do not produce as much of the solvent. 
Determination of the Hydrogen ion Concentration 
Since the reactions (acidity or alkalinity) of the various portions of 
the alimentary tract play an important part in determining how much 
arsenate of lead will be dissolved, the writer first determined the hydro¬ 
gen ion concentrations of the various portions of the digestive tract. 
These portions were as follows—(1) the oesophagus, (2) the honey 
stomach plus the stomach, and (3) the remainder of the alimentary tract. 
The divisions were made in this manner because these portions are more 
or less shut off from their neighboring sections, while there is free com¬ 
munication for the gastric juices within the portions themselves. 
The determinations w T ere made as follows. Twenty-four bees were 
killed with chloroform and immediately dissected. The oesophagi of 
these bees were removed and placed in 12 c.c. of neutral water (Ph + 
7). The honey stomach and stomach were treated in a similar manner 
and placed in a second flask containing 12 c.c. of the neutral water. 
The remainders of the alimentary tracts were placed in a third flask 
also containing 12 c.c. of the neutral water. At the end of an hour a 
sample was taken from each flask and tested with Phenol Red, Methyl 
Red and electrically. The solutions remaining in the flasks were kept 
24 hours at about 15 C° and tested again by the same methods. The 
results of these tests are shown in the following table. 
Portions of the Tract Immediate Reaction Reaction End of 24 hrs. 
Oesophagi. 7.0 7.0 
Honey stomachs 
-f 5.6 5.6 
Stomachs 
Intestine. 7.4 7.4 
Neutral Water. 7.0 7.0 
The second tests were made to see whether the solutions could stand 
in a cool room 24 hrs. without affecting their reactions. This point is 
very important, for in making the solubility tests the arsenate of lead 
was acted upon for 24 hrs. If during this time there was an increase 
in the acidity or alkalinity due to the decomposition of the tissues, 
then the solubility would be greater than under normal conditions and 
so give misleading results. As the table shows there was no change in 
the Ph + at the end of the 24 hrs. 
Solubility Tests 
In making the solubility tests, twenty bees were chloroformed, im- 
