1936] Toxicity of Trimethylamine for N ecrophorus 39 
The graph (Fig. 1) indicates a little more clearly the 
relation between toxicity and the various concentrations of 
the chemical. It appears that at high concentrations death 
occurs very rapidly, but that as the concentration decreases 
the toxicity becomes less. Moreover, the toxicity decreases, 
not in direct proportion to the concentration, but in a kind 
of geometric proportion. At very low concentrations (1%) 
the beetles can withstand the fumes for a long time. 
The objection may be raised that the data here given do 
not represent the toxicity of given concentrations of sub- 
stance, but the time required for the substance to reach a 
toxic concentration in an inclosed space. But this is chiefly 
an academic objection. If seventy minutes are required for 
a 1 % solution of trimethylamine to fill 125 cc. of space with 
enough gas to kill a beetle, the result is practically the same 
as if a low concentration, held constant, brought about the 
same result. The effect is the same in either case. 
There is some indication that, in low concentrations, tri- 
methylamine actually attracts Necrophori. Several speci- 
mens kept in an experimental cage, were trapped twice as 
frequently with this as with pure water. Beetles also tore 
a piece of cotton soaked with the chemical and left in their 
cage. 
Dead bodies lying in the open must be comparatively free 
from high concentrations of so volatile a substance as tri- 
methylamine. In a confined space the situation is different. 
It is the custom of collectors to trap necrophilous beetles in 
jars sunk in the earth and containing scrap meat. In such 
jars Necrophori, as well as other beetles, are often found 
dead, even when the decaying flesh is not sufficiently liqui- 
fied to produce drowning. Such jars have a strong odor of 
ammonia, which doubtless, in many cases, is due to the pres- 
ence of trimethylamine. 
