The sawfly Monophadnus longicornis (HTG, 1837)(Hymenoptera: Tenthredinidae) has been recognized in great numbers at Helleborus niger L. (Ranunculaccae) in Southeast Carinthia in 1984-91. The adults have been watched earliest between 1-25th of April, sometimes at first at the beginning of May, they feed a little bit on the petales of the christmas-rose. The larvae feed the epidermis of leaves, further they produce holes in the leaves on christmas- rose, in other countries also on bear's foot (H. focetidus L.) or on H. viridis L. There are described the way of egglaying, the stages of larvae and some ecological circumstandes
