How Sugar Quality and Concentration Influence Oviposition Preference in Drosophila Melanogaster.

Female insects possess a complex chemosensory system that enables them to identify optimal oviposition substrates for their developing offspring. Both calorie-rich and protein-rich substrates are particularly attractive for laying eggs. We hypothesize that females detect concentrations of sweet compounds and preferentially select those concentrations that enhance larval survival. To test this, we investigated how female Drosophila melanogaster evaluate substrates with varying concentrations of sugars and amino acids, and whether these preferences correlate with larval survival. Using choice assays, we found that females preferentially deposited eggs on substrates containing 0.1 mol/L sucrose, while higher concentrations (2 mol/L) were consistently avoided-a response not attributable to differences in substrate hardness or prior feeding experience during mating. In contrast, when presented with monosaccharides, females favored intermediate concentrations: 0.5 mol/L for both glucose and fructose, with a marked overall preference for fructose even when combined with an amino acid mixture. Moreover, substrates aligning with the females' oviposition choices often supported best survival of larvae. These findings indicate that female flies assess not only the concentration but might also consider the chemical nature of sweet compounds when making oviposition decisions and they underscore a critical link between maternal site selection and larval development.