Neotype designation and re-description of Prolachlanius resinatus (Hagen) (Neuroptera, Hemerobiidae) from Baltic amber, with the first record of the species from Rovno amber.

Prolachlanius resinatus (Hagen) is re-described, based on five specimens from late Eocene Baltic amber (including the neotype designated herein) and the first recorded specimen from contemporaneous Rovno amber (Klesov locality). This is the most common species of Hemerobiidae in Baltic amber. The forewing venation of Prolachlanius is most similar to that of Sympherobius, and, therefore, its assignment to Sympherobiinae is confirmed. The genus differs from other Sympherobiinae by the distal branch of RP being not deeply forked, and the presence of crossvein 4r-m in the forewing. The male genitalia of Prolachlanius are sufficiently dissimilar from those of other Sympherobiinae to distinguish it as a separate genus, particularly by the structure of the ectoprocts, and the 8th and 9th sternites. The extremely short eighth sternite of Prolachlanius is especially noteworthy.