Unearthing underground predators: The head morphology of larvae of the moth lacewing genus Ithone Newman (Neuroptera: Ithonidae) and its functional and phylogenetic implications

Abstract

Moth lacewings (Ithonidae) are a rare group of Neuroptera with an unusual subterranean larval life‐style. We examined external and internal head structures of an older‐instar larva of Ithone Newman with a broad spectrum of techniques. Larval autapomorphies, likely correlated with the subterranean habits, are the compact and shovel‐shaped head, unusually massive mandibular‐maxillary stylets, and a C‐shaped postcephalic body. Other cephalic autapomorphies are the massive X‐shaped tentorium, incurved antennae, and a strongly developed M. verticopharyngalis. The visual organs are distinctly simplified but a single functional stemma on each side of head is retained despite of the subterranean habits. In contrast to previous studies, a well‐developed gular sclerite is present in Ithonidae, possibly a secondary acquisition. A cephalic gland complex and poison channel are present, with an unexpected additional lateral accessory gland and an additional lateral channel. The poison glands and dual channels very clearly indicate that the larvae are predators, contradicting the phytophagous habits formerly postulated. Compared with soil‐inhabiting scarabaeoid beetle larvae, striking differences of head structures are due to different feeding habits and phylogenetic constraints. Morphological similarities like a C‐shaped postcephalic body and strongly developed legs suitable for burrowing in soil are evolutionary parallels associated with the subterranean life‐style in the two non‐related groups. Bayesian phylogenetic analysis was carried out with an updated morphological matrix. The results were compared with a phylogeny based on anchored hybrid enrichment data. The evolutionary transformations of selected characters were evaluated using phylogenies estimated from both datasets.

Cephalic anatomy highlights morphological adaptation to underground habitats in a minute lacewing larva of Dilar (Dilaridae) and conflicting phylogenetic signal in Neuroptera

“…The stout antenna with strengthened antennomeres 1 and 2 is another potential autapomorphy of Dilar and is likely to be correlated with the subterranean lifestyle of the larvae. This is in distinct contrast to other groups with slender and apparently delicate larval antennae (Wundt, 1961;MacLeod, 1964;Beutel et al, 2010a;Badano et al, 2021;Li et al, 2022). The presence of M. scapopedicellaris lateralis/medialis in Dilar is a remarkable feature.…”

“…, 2019; Li et al. , 2022): Mantispinae feed on the eggs of spiders as larvae (Redborg & Macleod, 1985; New 1986; Redborg, 1998); Symphrasinae are ectoparasitoids of holometabolous larvae or pupae (Eggleton & Belshaw, 1992; Ardila‐Camacho et al. , 2021); and Berothinae are associated with termites (Tauber & Tauber, 1968; Brushwein, 1987; Minter, 1990; Möller et al.…”

“…The presence of a frontoclypeal sulcus, a welldeveloped tentorial bridge, paired mouthparts curved inwards, and a normal sized head of later instars are very likely to be ground-plan features of Neuroptera (e.g., Aspöck & H. Aspöck, 2007;Beutel et al, 2010a;Li et al, 2022;File S3: Figs. S1, S2 and S4).…”

“…The knowledge of the anatomy of Neuroptera has rapidly increased in recent years, with larvae covered in the works of Beutel et al (2010a), Jandausch et al (2018aJandausch et al ( , 2019, and Li et al (2022), and with adults reported in Beutel et al (2010b), Randolf et al (2013Randolf et al ( , 2014Randolf et al ( , 2017, Randolf and Zimmermann (2019), and Handschuh and U. Aspöck (2020).…”

Xenos vesparum(Strepsiptera: Xenidae)—A New Insect Model and Its Endoparasitic Secondary Larva

“…As the adult females of Stylopidia (i.e., all Strepsiptera with endoparasitic females) appear greatly simplified morphologically and retain characters of the previous endoparasitic larval stage, they were also discussed in terms of heterochronic development (e.g., Kinzelbach 1971, Kathirithamby 1989, Richter et al 2017, Chafino et al 2018. Overall, only a few detailed anatomical studies of the postcephalic body of holometabolous larvae exist (e.g., Yavorskaya et al 2015, Jandausch et al 2018, Jandausch et al 2019, Di et al 2022. A modern anatomical study on endoparasitic larvae of Strepsiptera is only available for Eoxenos laboulbenei De Insect Systematics and Diversity, 7(1), 4; 2023, 1-40 https://doi.org/10.1093/isd/ixad003 Research Peyerimhoff, 1919, which belongs to the basal strepsipteran family Mengenillidae (Tröger et al 2020).…”