Fine structures inside the PreLie operad

This article aims at a detailed analysis of the PreLie operad. We obtain a more concrete description of the relationship between the anticyclic structure of PreLie and the generators of PreLie as a Lie-module, which was known before only at the level of characters. Building on this, we obtain an inclusion of the cyclic Lie module in the PreLie operad. We conjecture that the image of this inclusion generates an interesting free sub-operad.