Oleic acid is an example of a subgroup of lipids known as fatty acids. The article ‘ Effectiveness of Oleic Acid as a Bug Repellent against the Rice Flour Beetle’ describes an investigation into the function of oleic acid as an insect repellent. This was done by observing the effect of the presence of oleic acid on the behaviour of rice flour beetles with respect to rice flour, a favourite food of theirs.
Oleic acid is a known chemical released in the form of pheromones by certain insects upon death. Insects identify this hormone by its scent, and it signifies death and the possibility of disease to them. Insects avoid the source of this scent and so oleic acid is an effective repellent. Despite the effect it has on insects, it smells no worse than cooking oil to humans, and is also considered nutritious. This and its cost makes oleic acid a possible solution to the threat of insects attacking an infecting grain sources for humans.
In the article by Suman Mulumudi, the described experiment involves samples of either pure rice flour or rice flour mixed with oleic acid separately being made available to a number of rice flour beetles. The described behaviour of the beetles reflected the expectations, as the samples without oleic acid were attacked constantly, while the samples without were attacked occasionally, with the beetles moving away quickly after, expressing their distaste for the additional ingredient, and giving the flour samples a berth.
The article expresses that the experiment successfully illustrated the effectiveness of the oleic acid in repelling the beetles, though an alternative method would need to be found than mixing the oleic acid into the flour that would be later consumed by humans. Means such as a gelatinous cube or packet of oleic acid to saturate the air within flour containers with the scent were suggested as possibilities, and if applied, they may very well greatly affect the success in preserving flour and other grain food sources from these pests.
References : http://www.wisegeek.org/what-is-oleic-acid.htm