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In the early 70s, the soil biologist Marcel Bouché classified French earthworms species into defined ecological categories. This classification system was immensely successful and is still widely used to describe earthworm functional groups even outside of Europe. Bouché used morpho-anatomical traits to differentiate three main categories: epigeic, anecic and endogeic. However, the way species are assigned to a category was not explicitly described in Bouché’s work. Thus, some earthworm species can still be assigned to two categories depending on the way researchers interpret Bouché’s description. To solve these issues and avoid unnecessary controversies, we applied PCA and random forest models to the seminal data of Marcel Bouché (earthworm morpho-anatomical traits). Their assignment to Bouché’s three main categories allowed us to statistically redefine the different categories and determine which …