In adult fruit flies, Drosophila, a group of neurons was discovered whose activation leads to a feeling of hunger. If these neurons are artificially forced to send signals, even well-fed fruit flies begin to eat again - but only if it is right in front of them, such flies do not begin to look for food. During the activation of these cells, Drosophila prefer food rich in energy. The neurons of this group secrete mainly serotonin and affect the functioning of most parts of the Drosophila brain.