1958 ] Wilson, Durlach, Roth — Chemical Releasers 113 
out and dropped at the same place. Five hours later all of 
the treated squares had been moved to a position about 
twenty centimeters beyond the nest edge. A saevissima 
worker was later seen carrying a treated square back and 
forth in the restless fashion commonly seen in workers of 
this species carrying corpses. 
Assay of extract from another insect species. To deter- 
mine whether fatty extracts of corpses of another insect 
species causes the neerophoric response in Pogonomyrmex 
badius, extracts from meal worms ( Tenebrio molitor) al- 
lowed to decompose in open air for two weeks were tested 
in the usual fashion. Treated paper squares were carried 
promptly to the refuse piles by the Pogonomyrmex workers, 
whereas control squares were left untouched for the first 
several hours. The behavior of the ants toward the treated 
squares seemed identical to that shown toward squares 
treated with the extract of Pogonomyrmex corpses. 
Conclusions 
Pogonomyrmex badius workers utilize a relatively lim- 
ited range of stimuli in “recognizing” insect corpses. More- 
over, the stimuli appear to be exclusively chemical in 
nature. One of the principal chemical releasers is evidently 
the fatty acid that accumulates in the bodies of sister work- 
ers allowed to decompose in open air. An ester may also 
play a secondary role. Of several chemical compounds test- 
ed commonly found in insect corpses, oleic acid was the 
only substance which caused the ants to behave as they 
do toward dead insect bodies. Whether other substances 
present in ant corpses (and those of other animals) re- 
lease the neerophoric response is not known. It may be 
suggestive that the common smaller molecular products of 
decomposition thus far tested have all produced neutral 
or alarm behavior without any element of necrophoresis. 
It is also noteworthy that long-chain fatty acids are chem- 
ically among the most stable and least volatile of fat and 
protein decomposition products and hence tend to accumu- 
late disproportionately in insect corpses. As a result these 
substances have the potential to serve as efficient signals 
of the presence of aging corpses, as opposed to freshly 
