Estimates of the worldwide post-harvest insect pests’ loss of foodstuffs (especially stored grains) may amount to 5-10% in the temperate zone and 20-30% in the tropical zone. Like wise, in Ethiopia loss of stored produce reached up to 20-30 %. Such damage may reach 10 to 40% in countries where modern storage technologies have not been introduced. Which groups of insects harboring the most economically important groups? Why Semiochemicals are preferable to conventional pesticides? What does it mean primary and secondary pest? Why Semio-chemicals are the promising alternative that could be used to control insect pests by behavioural manipulation: in the form of sex pheromone lures for monitoring, mass trapping, attracting and killing, mating disruption of insect pests? This work briefly responds all the mentioned questions and more.