Life cycle, population dynamics

• The Drosophila spp. present 6 to 8 annual generations. Their biology is not well known, but it seems to be closely linked to human activity since no form of winter conservation has been recorded in our latitudes.

• The complete cycle from egg to adult is quite rapid, in the order of 10 to 20 days. Their presence is observed in spring and summer, it is always more important during the ripening of the various fruits that attract them.

• Close to the maturity of the grape, the adults (figure 1) are attracted by the volatile odors given off by the berries. These odors are released following parasitic or accidental injuries to the grapes. The seeps are used as food for the fruit flies which, at the same time, bring on their body (figures 2 and 3) and reject during their nutrition various microorganisms including those associated with acid rot. The females then lay their eggs fertilized on the berries.

• The larvae hatch quickly, after 24 hours. They then feed on the complex mixture of yeast-bacteria and the fermentation medium. Three larval stages follow one another in the berries until pupation (formation of a pupa ) on site and then the appearance of adults who will mate and have the capacity to contaminate new berries.
  Feeding the larvae promotes the shredding of berry tissue. Their faeces, containing the microorganisms, will amplify the development of volatile acidity, attracting new adults.