Hi, thanks so much for your interest!

So flies can get 'drunk' from drinking alcohol, in the sense that they are typically sleepier or move more slowly, but typically they stop before it has too detrimental of an effect on their behaviour, most likely for the predator issue but also to allow them to continue egg laying, finding a mate etc. There are a few studies showing that if flies are exposed to a high concentration of alcohol over a period of time, they can become more tolerant to it - similarly to humans!

Alcohol and similar ethanol products are readily available in the wild. Metschnikowia pulcherrima yeasts typically live on rotting fruit and produce chemicals like ethanol and 2-phenylethanol as a result. This is what we think attracts flies to lay their eggs there, possibly for its self-medication properties! Despite our lab fly populations being kept captive for decades, and therefore not experiencing wild yeasts like M. pulcherrima, they are still showing a preference for this species and the alcohol products above other yeast species. This suggests it is a beneficial trait to remain in the flies throughout the generations, and suggests a more significant purpose! So that's what I'm trying to understand with my research!

Any other questions let me know!