To verify the questionable description of sperm structure of Trichogramma dendrolimi, in relation to Chalcidoids, a reinvestigation was undertaken. The spermatozoa appear wavy along their entire length. A small acrosome, together with the anterior nuclear region, is surrounded by an extracellular sheath, from which filaments radiate. The nucleus is helicoidal and attached to the flagellum by a centriolar adjunct. The axoneme has the 9 + 9 + 2 microtubule arrangement pitched in a long helix, with the spiralling mitochondrial derivatives coiling around it. Therefore, the spermatozoa of T. dendrolimi are very similar to those of other chalcidoids and different from the first description. It is now possible to affirm that the helical sperm structures are an apomorphic homology for Trichogrammatidae as well as Eulophidae, Pteromalidae, Eurytomidae, Torymidae, Mymaridae and for some other chalcidoids, if not all.822159164