The Morphological Diversity of Dragon Lacewing Larvae (Nevrorthidae, Neuroptera) Changed More over Geological Time Scales Than Anticipated

SIMPLE SUMMARY: Nevrorthidae is the group of dragon lacewings, an ingroup of lacewings (Neuroptera). Nevrorthidae has often been considered a relic group. Today, dragon lacewings are known in a few regions with rather large distances between them, with some species occurring in southern Europe, Japan, Australia, and one in China. Fossils in amber from the Baltic region (c. 35–40 million years old) and Myanmar (c. 100 million years old) support the idea that this distribution is only a remnant of an originally larger distribution. Larvae of the group are slender and elongated and live mostly in water. Yet, larvae are in fact very rare. So far, only slightly more than 30 larval specimens have been depicted in the literature, including all extant and fossil larvae. Here, we report numerous additional specimens, including extant larvae, but also larvae in Baltic and Myanmar amber. Together with the already known ones, this sums up to over 100 dragon lacewing larvae. We used quantitative methods to study the morphology of these larvae and compared these results over time to identify changes in the diversity. Although there are now more specimens in the data set, it is still unbalanced; for example, newly hatched larvae (several dozen specimens) are only known from Baltic amber. We expected little change in the morphology of the larvae over geological time, as indicated by earlier studies. However, on the contrary, there are morphologies present in fossil larvae that are now extinct. This result is similar to that for other groups of lacewings which have a relic distribution today, as also in larvae of these groups, there is a lower diversity today than in the past. ABSTRACT: Nevrorthidae, the group of dragon lacewings, has often been considered a relic group. Today, dragon lacewings show a scattered distribution, with some species occurring in southern Europe, Japan, Australia, and one in China. The idea that this distribution is only a remnant of an originally larger distribution is further supported by fossils of the group preserved in ambers from the Baltic region (Eocene, ca. 35–40 MaBP) and Myanmar (Kachin amber, Cretaceous, ca. 100 MaBP). Larvae of the group are slender and elongated and live mostly in water. Yet, larvae are in fact very rare. So far, only slightly more than 30 larval specimens, counting all extant and fossil larvae, have been depicted in the literature. Here, we report numerous additional specimens, including extant larvae, but also fossil ones from Baltic and Kachin amber. Together with the already known ones, this sums up to over 100 specimens. We analysed quantitative aspects of the morphology of these larvae and compared them over time to identify changes in the diversity. Despite the enriched sample size, the data set is still unbalanced, with, for example, newly hatched larvae (several dozen specimens) only known from the Eocene. We expected little change in larval morphology over geological time, as indicated by earlier studies. However, on the contrary, we recognised morphologies present in fossils that are now extinct. This result is similar to those for other groups of lacewings which have a relic distribution today, as these have also suffered a loss in diversity in larval forms.