Animal diet is generally shaped to the availability of food resources and to the animal ability to detect and assimilate nutriments. Animals with highly specialized diets are often encountered in poor environments where they have developed peculiar physiological adaptations 
such as in «plant-insect» or «/parasitoid relationships 
. In contrast, species with a generalist diet such as Drosophila melanogaster
often show a much widespread ecological and geographic distribution.
To survive, animals need to ingest essential nutriments that they cannot synthesize. This includes essential fatty-acids (FAs) such as omega-6 FAs in human diet 
, even if their effects have not been yet fully elucidated 
. However, and despite a strong link between severe dietary based etiologies (obesity, cancer, vascular) and excessive FA consumption, a limited effort was brought to explore the link between the sensory cues provided by FAs and feeding preference 
. Behavioral studies showed that rodents could discriminate a number of FAs based on their quality and concentration 
. Insects also show contrasted responses to FAs. For example, the adult mosquitoes Aedes aegypti
and Anopheles gambia
and the nymphal bug Triatoma infestans
are attracted by specific FAs combined with L-lactic acid, which are secreted by the human skin 
. In contrast, adult mosquitoes and flies may also be repulsed by FAs alone or combined with volatile substances 
Since vertebrate and invertebrate organisms show striking similarities in the organization and functioning of their chemosensory systems 
, the fruitfly D.
is a very useful model to dissect the genetic bases of feeding behaviors. If the biological mechanisms involved in the perception of sugar, salt, bitter substances or amino-acids have been largely explored both in larvae and adults 
, those underlying the perception of FAs received much less attention despite their evolutionary conservation. For example, the CD36 factor required for lipid binding and transport in mammals is also involved in the detection of a FA-derived pheromone in D. melanogaster
. Moreover, sequence similarities exist between members of the ML family of lipid-binding proteins, present in all eukaryotes 
, and the CHEB family of proteins specifically binding to Drosophila
FA-derived pheromones 
. However, Drosophila
response to pure FAs was rarely explored and the few experiments were only done in adults 
Using varied behavioral paradigms, involving groups and individuals, we measured the response of wild-type D. melanogaster larvae and adults of both sexes to six pure saturated and unsaturated dietary FAs (from C14 to C18). We found that they are able to discriminate these FAs and change their preference during development.