Challenges for understanding lacewings: how to deal with the incomplete data from extant and fossil larvae of Nevrorthidae? (Neuroptera)

Abstract

Within Neuroptera, the group of lacewings, the ingroup Nevrorthidae is special in several aspects: 1) the group may represent the sister group to all other neuropterans; 2) the group is quite species-poor with only 19 extant species known so far; 3) its representatives show a disjunct relict distribution; 4) it has very unusual appearing larvae. These larvae are very elongate, almost worm-shaped. Our overall knowledge of these larval forms is still very limited. We here review all known occurrences of extant larvae, amended by fossil larvae, all preserved in amber. So far there have been only 17 extant larval specimens of Nevrorthidae depicted in the literature. We also present new fossil larvae, with this reaching a total number of 16 known fossil larvae of Nevrorthidae. When plotting measured lengths, larvae cluster into more than three clusters. Also reconstructed size gains between these clusters indicate that Nevrorthidae might in fact develop through more than three larval stages, unlike other lacewings. A special subdivision of the trunk segments observed in many larvae indicates a specialisation for moving in confined spaces. Comparison of syn-inclusions and literature data make it likely that not all larvae lived in running waters, as previously assumed. Overall our knowledge remains rather limited, yet the data allow to draw some new conclusions about the life and evolution of these larval forms.

Long-headed predators in Cretaceous amber—fossil findings of an unusual type of lacewing larva

“…In long-necked antlions (larvae of the group Crocinae) this is achieved most prominently by the elongate sclerotised cervix, which in some forms can only be described as astonishingly long (see recent summary in Herrera-Flórez et al, 2020a). However, it is in fact not only the cervix that contributes to the length in some larvae, but also the prothorax (see discussion for the problem of neck versus prothorax in Haug, J.T. et al, 2020a).…”

Changes in the Morphological Diversity of Larvae of Lance Lacewings, Mantis Lacewings and Their Closer Relatives over 100 Million Years

“…Cases in which the same specimen had been re-figured were also included chronologically with reference to the original occurrence. While this includes a certain redundancy, it should represent the most complete way of cross-referencing, avoiding interpreting the same specimens as two independent occurrences (this way of presentation has also been used for other ingroups of Neuroptera [6,[15][16][17]). For an easier cross-reference to our dataset, we provide the dataset number here along with the specimen.…”

“…(1) Takahashi [92] reported a larva and interpreted it as a larva of Dilaridae. Later studies demonstrated that this larva is one of the group Nevrorthidae, hence most likely of Nipponeurorthus (see recent discussion in [6]). Therefore, the specimen could not be further considered here.…”

“…It may therefore not be surprising that many lacewings possess strongly curved stylets, as do the larvae of antlions (Myrmeleontidae), owl "flies" (should better be termed owl lacewings for consistency; Ascalaphidae), spoon-winged lacewings (Nemopterinae), splitfooted lacewings (Nymphidae), long-necked antlions (larvae of thread-winged lacewings; Crocinae), long-nosed antlions (larvae of silky lacewings; Psychopsidae), aphid lions (larvae of green and brown lacewings; Chrysopidae and Hemerobiidae), and even the aquatic larvae of Nevrorthidae (no vernacular name for representatives of this rather species-poor group). Yet, in the latter, the stylets are slightly special in being rather straight proximally, but strongly curved distally [6].…”

Fossil dragonfly-type larva with lateral abdominal protrusions and implications on the early evolution of Pterygota

“…Based on the developed armature already this cuticle must have been at least from a stage 3 larva (see discussion in Schädel et al., 2020 for problems with the counting system of stages); the holotype is a stage 4 larva. The new specimen should therefore at least represent a stage 5 larva; based on the size differences it could even represent a stage 6 larva, as the size increase from the stage 4 larva to this specimen is relatively larger than from the presumed stage 3 to the stage 4 larva (for discussions on the relative size increase from one stage to the next, see Legaspi et al., 1994 ; Kutschera et al., 2012 ; Haug et al., 2020 ).…”