[Supernumerary morphogenesis in the leg of the stick insectCarausius morosus Br.]

The local conditions of appearance of a supernumerary morphogenesis and its characteristics (composition, localisation, orientation), have been studied in the leg of the stick InsectCarausius morosus. 1) A 180° rotation of the trochanter around the proximo-distal axis before reimplantation in the coxa corresponds, between these two joints, to a disharmony of orientation in the two planes antero-posterior and dorso-ventral. It provokes the formation of an axial regenerate rotated by 180°, issued from the trochanter, and of 1, 2 or 3 supernumerary branches. These grow generally at the joining level between coxa and trochanter. Their relations of symmetry with the axial regenerate are analyzed. 2) The graft of a trochanter on the symmetric coxa after a 180° rotation or not, which corresponds to a disharmony of orientation in the planes antero-posterior or dorso-ventral, determines in 75% of the cases the growth of two supernumerary structures. These are located in the plane of disharmony, on each side of the axial regenerate, that is to say where two normally opposite sides are artificially put in contact and constitute a heterogeneous association. 3) The heterogeneous associations obtained in grafting one coxal side on an opposite coxal side trigger a supernumerary morphogenesis on the receptor side, even on a complete leg. 4) These results allow to consider as a working hypothesis that the morphogenesis is triggered by an incompatibility between the tissues of the opposite sides. This hypothesis is discussed in the light of recent results obtained in the insects and more generally in the invertebrates.