The Mediterranean fruit fly, Ceratitis capitata , is one of the most injurious pests attacking more then 300 fruit species and widely spread around the world. The development of food baits to attract fruit flies has begun over a century ago in parallel with the use of poison-bait sprays to control fruit flies. A breakthrough in the development of baits was McPhail's findings that decomposing proteins are attractive to fruit flies. His findings were the basis for the development of the commercial protein-based baits. The rational behind the attraction to a source of protein is mainly the specific hunger of females for an exogenous supply of protein needed for the maturation of the ovaries, which is a general feature in Diptera.
Ammonia is the most significant volatile breakdown product of protein decomposition.
The efficiency of ammonia in the attraction of fruit flies remained unclear despite the use of ammonia-releasing compounds as baits. Measurement of the attraction of the females toward pure aqueous solutions of ammonia with increasing concentrations and in parallel determination of the rate of ammonia released from the same solutions showed a clear correlation between the two parameters. Higher levels of release rate are repellent to the females. Several comparisons between the attraction of different sources of ammonia such as ammonium salts, commercial liquid baits and manures and their ammonia release rate pointed to the presence of additional attractive components. The continuation of the present research focuses on the discovery of these components among volatile breakdown products of amino acids.