An invasive sawfly Aproceros leucopoda Takeuchi, 1939, which originates from East Asia, has colonized elms (Ulmus spp.) in Austria, Hungary, Poland, Romania, Slovakia and the Ukraine, at least since 2003. In Europe, the larvae can completely defoliate native and non-native elm trees and may cause at least partial dieback. Field observations indicate that elms are infested independent of their age and site characteristics. The life cycle of A. leucopoda is described based on material reared in Hokkaido, Japan. Parthenogenetic reproduction, short life cycle of summer generations and the ability to produce four generations per year result in the production of numerous progeny. The evolution of a seasonal dimorphism in head morphology, a simple cocoon that is attached directly to the host plant and a short period spent in the cocoon stage during summer, are putative apomorphies shared by Aproceros Takeuchi, 1939 and Aprosthema Konow, 1899. These traits reduce developmental costs and contribute to the proliferation of A. leucopoda. No specialized parasitoid, that can effectively reduce outbreaks of this species, is known. It is likely that this pest will spread into central and south-western Europe. Further monitoring of A. leucopoda is required to assess future range extensions in Europe, its exacerbating effect on Dutch elm disease and to find a suitable biocontrol agent. Concise keys to imaginal and larval stages are presented that will facilitate the identification of A. leucopoda.
Concordant differences in morphology, phenology and RAMS markers, as well as in sequenced mtDNA (COI, COII, cytb) and nuclear DNA (ITS2) fragments, indicate that Dolerus asper Zaddach, 1859 and Dolerus brevicornis Zaddach, 1859 are valid species. On the basis of morphology, molecular markers, and distributional records, both species are distinct from Dolerus gibbosus Hartig, 1837 (= Dolerus planatus Hartig, 1837). Taxonomy of the species is clarified and the neotypes of Dolerus asper Zaddach, 1859 and Dolerus brevicornis Zaddach, 1859 are designated. The synonymies of Dolerus asper Zaddach, 1859, to Dolerus planatus Hartig, 1837 and Dolerus derzavini Malaise, 1931, spec. rev. to D. asper Zaddach, 1859 are abandoned. Dolerus carbonarius Zaddach, 1859 and Dolerus fumosus Zaddach, 1859 are considered to be species inquirendae. Phylogenetic analyses of the ITS2 fragment and fragments of ITS2 + COI and ITS2 + COII yielded the topology [D. asper, (D. brevicornis, D. gibbosus)], while those of all other markers and their combinations resulted in the topology [D. brevicornis, (D. asper, D. gibbosus)]. In the latter hypothesis the clade asper + gibbosus is also supported by structural synapomorphies.