While hot days have led to a multiplication of the number of foreign species invasions, emblematic invertebrates of plain rivers, generally known for their proliferation, are disappearing without known cause. The recognition of massive hatchings of mayflies, as well as their exploitation, bears witness to their interest to us: spectacular mass-swarmings for some, aberrant or intrusive to others, the emergence of aquatic insects into a multitude of winged adults is known as “manna” – a well known phenomenon to fishermen, as well as to the residents along the Great Saône, who in season, will exploit their falls for economic benefits. The manna is something that is expected, even if it recurs only sporadically, and thus when absent, brings into question the development of the Saône’s river and of its basin and the possible ecological consequences of these. [Article in French]
Césard, N., Brulin, M. 2011. Les mannes d’éphémères, Insectes, OPIE-INRA, n° 160 (1), pp. 13-16.
Césard, N. 2010. Vie et mort de la manne blanche des riverains de la Saône. Etudes rurales, 185, pp. 83-98.