The gastrointestinal tract has recently come to the forefront of multiple research fields. It is now recognized as a major source
of signals modulating food intake, insulin secretion and energy balance. It is also a key player in immunity and, through its interaction with
microbiota, can shape our physiology and behavior in complex and sometimes unexpected ways. The insect intestine had remained, by
comparison, relatively unexplored until the identification of adult somatic stem cells in the Drosophila intestine over a decade ago. Since
then, a growing scientific community has exploited the genetic amenability of this insect organ in powerful and creative ways. By doing
so, we have shed light on a broad range of biological questions revolving around stem cells and their niches, interorgan signaling and
immunity. Despite their relatively recent discovery, some of the mechanisms active in the intestine of flies have already been shown to be
more widely applicable to other gastrointestinal systems, and may therefore become relevant in the context of human pathologies such as
gastrointestinal cancers, aging, or obesity. This review summarizes our current knowledge of both the formation and function of the
Drosophila melanogaster digestive tract, with a major focus on its main digestive/absorptive portion: the strikingly adaptable adult midgut.