Systematic position of Eulachnus cembrae Borner with description of hitherto unknown sexual morphs of E. pumilae Inouye (Hemiptera, Aphididae, Lachninae)

The identity of Eulachnus cembrae Borner, 1950, stat. rev. from Europe, treated as a synonym of E. pumilae Inouye, 1939 from East Asia is clarified based on characters of sexual morphs. The oviparous female and alate male forms of E. pumilae are described and figured in detail for the first time and the poorly known sexual forms of E. cembrae are redescribed and figured in detail as well. Sexual morphs of the two similar species are compared, and significant differences clearly distinguishing those species are presented. A key to the identification of oviparous females and males of E. cembrae and E. pumilae as well as notes on host plants and distribution of these species are provided. The status of E. pumilae in the European aphid-fauna is clarified. Morphological characters of the sexual generation that may be useful for species identification are discussed.