Neuroptera, the group of lacewings, comprises only about 6000 species in the modern fauna, but is generally assumed to have been more diverse and important in the past. A major factor of the modern-day ecological diversity of the group, and supposedly in the past as well, is represented by the highly specialised larval forms of lacewings. Quantitative analyses of the morphology of larvae revealed a loss of morphological diversity in several lineages. Here we explored the diversity of the larvae of mantis lacewings (Mantispidae), lance lacewings (Osmylidae), beaded lacewings (Berothidae and Rhachiberothidae, the latter potentially an ingroup of Berothidae), and pleasing lacewings (Dilaridae), as well as fossil larvae, preserved in amber, resembling these. We used shape analysis of the head capsule and stylets (pair of conjoined jaws) as a basis due to the high availability of this body region in extant and fossil specimens and the ecological importance of this region. The analysis revealed a rather constant morphological diversity in Berothidae. Mantispidae appears to have lost certain forms of larvae, but has seen a drastic increase of larval diversity after the Cretaceous; this is in contrast to a significant decrease in diversity in adult forms.

Aphidlions are larvae of certain lacewings (Neuroptera), and more precisely larvae of the groups Chrysopidae, green lacewings, and Hemerobiidae, brown lacewings. The name ‘aphidlion’ originates from their ecological function as specialised predators of aphids. Accordingly, they also play an economic role as biological pest control. Aphidlions have, mostly, elongated spindle-shaped bodies, and similarly to most lacewing larvae they are equipped with a pair of venom-injecting stylets. Fossils interpreted as aphidlions are known to be preserved in amber from the Cretaceous (130 and 100 million years ago), the Eocene (about 35 million years ago) and the Miocene (about 15 million years ago) ages. In this study, new aphidlion-like larvae are reported from Cretaceous amber from Myanmar (about 100 million years old) and Eocene Baltic amber. The shapes of head and stylets were compared between the different time slices. With the newly described fossils and specimens from the literature, a total of 361 specimens could be included in the analysis: 70 specimens from the Cretaceous, 5 from the Eocene, 3 from the Miocene, 188 extant larvae of Chrysopidae, and 95 extant larvae of Hemerobiidae. The results indicate that the diversity of head shapes remains largely unchanged over time, yet there is a certain increase in the diversity of head shapes in the larvae of Hemerobiidae. In certain other groups of Neuroptera, a distinct decrease in the diversity of head shapes in larval stages was observed.

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