A split-footed lacewing larva from about 100-million-year-old amber indicates a now extinct hunting strategy for neuropterans

Abstract

Lacewing larvae (Neuroptera) are, mostly, fierce predators, as prominently demonstrated by the widely known larvae of antlions. A key feature of lacewing larvae is the structure of their mouthparts: each upper jaw forms a distinct stylet with its corresponding lower jaw; hence each lacewing larvae bears a pair of stylets, which are far anterior on the head (prognathous). The stylets allow to pierce the prey, to inject neurotoxic venom followed by saliva, and finally the liquefied tissues can be sucked through the stylets (e.g. MacLeod 1964, Aspöck & Aspöck 2007, Zimmermann et al. 2019.Mostly the stylets are elongate and curved to allow a counteraction for penetrating the prey easier. In some larvae, the stylets are straight or even outward curved (e.g. MacLeod 1964). One larger ingroup of Neuroptera, Myrmeleontiformia, the group of antlion-like lacewings, is characterised by an additional specialisation of the stylets, namely teeth. Such teeth can be lost in some lineages; in some cases this is apparent during ontogeny (see discussion in Haug et al. 2019a). Among modern representatives, smaller teeth are known in some larvae of thread-winged lacewings (Crocinae; see discussion in Haug et al. 2021a) and spoon-winged lacewings (Nemopterinae; Monserrat 1996: p. 104, Haug et al. 2021b). Prominent teeth occur in larvae of the group Myrmeleontidae + Ascalaphidae (Badano 2012, Badano & Pantaleoni 2014a, b; monophyly of ingroups currently unclear, e.g. Machado et al. 2019, Badano et al. 2021 and also in larvae of split-footed lace wings (Nymphidae; e.g. MacLeod 1964, Haug et al. 2022a). Among the modern groups, there is a certain variation in the number of teeth, but three is rather common (MacLeod 1970: p. 165), besides in split-footed lacewings which usually have a single one (e.g.

Quantitative analysis of lacewing larvae over more than 100 million years reveals a complex pattern of loss of morphological diversity

“…Text 1 ), as already indicated 34 . Yet, in the Cretaceous there were numerous now extinct early offshoots of the larger group of antlion-like lacewings (Myrmeleontiformia 26 , 35 – 38 ) with heads and mouthparts to a certain extent comparable to those of modern owllion larvae; these similarities are detectable, for example, in bearing prominent teeth or in similar values in some of the principal components (PCs; especially PC1, but also PC2; Fig. 1 ).…”

An Expanded View on the Morphological Diversity of Long-Nosed Antlion Larvae Further Supports a Decline of Silky Lacewings in the Past 100 Million Years

“…Although the original study concentrated on head capsule shape [ 18 ], most follow-up studies on larvae of other lineages of Neuroptera have used the head capsule together with the stylets [ 17 , 19 , 20 , 21 , 24 , 25 , 26 , 112 ]. This analysis ( Figure 31 ) is also most comparable in its results to the earlier study.…”

“…Along lacewing larvae in the Cretaceous, indeed, many larvae already show very modern appearing morphologies, including indications of very modern types of behaviour [ 113 , 116 , 122 , 123 , 124 ]. Moreover, numerous highly aberrant forms are known [ 23 , 112 , 113 , 117 , 118 , 119 , 120 , 121 , 125 , 126 , 127 , 128 ].…”

The Diversity of Larvae with Multi-Toothed Stylets from About 100 Million Years Ago Illuminates the Early Diversification of Antlion-like Lacewings

“…Different structures of the larvae were considered and analysed with the aid of an elliptic Fourier transformation. The data set was based on the directly studied specimens and larvae from the literature, partly assembled from earlier datasets [44,83,84,[87][88][89], including all lacewing larvae that possess teeth. In total, 424 larvae were considered (for a specimen list, see table in Supplementary Materials), including:…”