Abstract Leptocybe invasa Fisher & LaSalle, a new genus and species of Eulophidae, displays thelytokous reproduction, forming typical bump-shaped galls on the leaf midribs, petioles and stems of new growth of several Eucalyptus species. Presently, this wasp occurs in large areas in the Middle East, the Mediterranean and Africa, and is a serious pest in young plantations. Heavy galling prevents further development of the infested growth. Leptocybe invasa is only known from females. Mean length of a gall containing a single wasp is 2.1 mm, leaves of intensively growing trees may carry over 50 galls per leaf. Mean development time from oviposition to emergence is 132.6 d in room temperature. In Israel the wasp produces two or three overlapping generations annually. Mean survival time for wasps fed with honey and water is 6.5 days. Ten species were found to be suitable hosts in Israel: E. botryoides, E. bridgesiana E. camaldulensis, E. globulus. E. gunii. E. grandis, E. robusta, E. saligna, E. tereticornis, and E. viminalis.