28 BULLETIN OF WISCONSIN NATURAL HISTORY SOCIETY. VOL. 4, NOS. 1-2. 
closed pipette and kept for an extended time at an exhaustion 
of about 300 mm., a number of small metallic, bluish-purple, 
spurred and acidulated scales and needles appear in the upper 
bulb of the tube. These lamellae appear pink by transmitted light. 
Although by their luster and volatile character they suggest iodine, 
they give no test for this element, and are probably a polymerisa- 
tion product, as they increase in number with time, even when 
kept at the ordinary pressure. 
Unfortunately, although our Spirobolus were very active at 
first — on one occasion a large specimen ejected a decided stream 
a distance of ten inches — they soon showed signs of weakening, 
and after about ten extraction, which gradually diminished in 
amount during the four months of experiment, their glands re- 
fused to reproduce their secretion, although the animals seemed 
otherwise in good condition, and we were forced to discontinue 
the interesting study. 
Although Loew suggested pyridine it was with' the under- 
standing that this odor might have come from the German alcohol 
used as the preservative. This must obviously be its source, as 
Spirobolus has quite a different odor. The facts brought forth by 
Dr. Cook as to the action of the air we have duplicated during 
our tests, and these can all be explained upon the idea of saponi- 
fication. It is not the final composition that is effective as the 
repelling agent, as he has suggested, but the condition that 
obtains just before decomposition. The unstable nature of the 
secretion gives it great reducing power, as can be shown with 
alkalinated silver iodide. Its staining effects recall the secretions 
of Brachynus, Platynus, and their related forms among the 
beetles, which insects Julus greatly resembles in smell, but in addi- 
tion to the staining principle these Carabidae produce formic and 
butyric acids, so the secretions cannot be identical. 
Experiments with Ants. 
A. The relative Amount of Formic Acid present in different 
Species. 
It has long been known that certain species of ants, e. g., 
Formica and Lasius, secrete a considerable amount of free formic 
acid. This is stored up in the sac which contains the acid part 
of the stinging fluid in those species of Ants which have well- 
developed stings, while in those devoid of stings it is retained in 
a special sac in the posterior part of the abdomen. The following 
experiments were conducted with a view towards determining 
