Morphology of the primary larva of Mantispa aphavexelte Aspöck & Aspöck, 1994 (Neuroptera: Mantispidae) and phylogenetic implications to the order of Neuroptera

Abstract

The external and internal morphology of the primary larva of Mantispa aphavexelte was studied and documented with a broad spectrum of techniques. The cephalic anatomy, which is very similar to conditions found in other neuropteran immatures, is mainly affected by the formation of specialized mandibulo-maxillary sucking tubes and associated internal features. The postcephalic anatomy largely follows a generalized holometabolan pattern, with well-developed muscles in the thorax and the abdominal segments, an elongate, uncondensed ganglionic chain, and well-developed Malpighian tubules. The phylogenetic analysis of 70 larval characters suggests a weakly supported clade comprising Dilaridae, Berothidae, Rhachiberothidae and Mantispidae. Mantispoidea comprising Rhachiberothidae, Berothidae and paraphyletic Mantispidae is suggested by overlapping scales on antennae and maxillae, thoracic “trichobothria”, and hypermetamorphosis with scarabaeiform 2nd instar larvae. The relationships of the mantispoid terminals are not resolved, and Mantispa (Mantispinae) and Plega (Symphrasinae) are not retrieved as sister taxa. Spider parasitism and feeding in spider egg sacs is characteristic for Mantispinae, whereas immatures of Berothidae and non-mantispine mantispid larvae prey on the offspring of social or non-social aculeatan Hymenoptera, on termites, or on immatures living in soil or under bark, for example scarab larvae. Specializations of the legs like a trumpet-shaped empodium and a fixed tarsal pseudoclaw, enable mantispine larvae to cope with functional challenges linked with their specialized form of parasitism, like entering a host or penetrating its egg sack. The largely immobilized and straight sucking stylets are suitable for piercing eggs of spiders, but not for grasping prey. The terminal eversible attachment structure probably provides anchorage of the abdominal apex and thus may facilitate the penetration of the egg sac or membranes of the body surface of a spider. It may also facilitate boarding a passing suitable host. Very small size of the 1st instars and hypermetamorphosis are likely linked with parasitism. Even though the primary larvae of M. aphavexelte belong to the smallest immatures in Neuroptera, the effects of miniaturization are very limited.

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

“…Even though it cannot be completely excluded that this is a strongly shifted and modified cephalic gland, the completely different location, anterior clypeal area versus lateral cephalic region posterior to the mouthparts (e.g., Jandausch et al, 2019), makes homology very unlikely, even though our datasets did not reveal external openings. It is safe to say that gland-like structures with a similar position have not yet been observed in any other neuropteran larvae (e.g., Wundt, 1961;Rousset, 1966;Beutel et al, 2010a;Jandausch et al, 2018aJandausch et al, , 2019. Consequently, the presence of these structures is a potential autapomorphy of the family.…”

“…These intrinsic muscles, which belong to the ground plan of Hexapoda, have not been found in any other holometabolous larvae yet (e.g., Beutel et al, 2009). This also includes other groups of Neuroptera (Wundt, 1961;Beutel et al, 2010a;Jandausch et al, 2018aJandausch et al, , 2019Zhao et al, 2020;Li et al, 2022), even though Rousset (1966) mentioned the possible presence of a very thin scapopedicellar muscle in a larva of Chrysopa Leach. The intrinsic antennal muscles are likely to contribute to the mobility of the antennae, and possibly enhance the ability to perceive motion, direction, and distance in soil.…”

“…The terminology for the skeleton generally follows that of Beutel et al (2010a) and Jandausch et al (2018aJandausch et al ( , 2019, whereas that of the muscles follows v. Kéler (1963).…”

“…Straight and parallel or subparallel paired mouthparts is an unusual feature. However, the mandibulo-maxillary stylets vary considerably in shape among the four families in question, with straight mesal margins in Mantispinae and Drepanicinae (Dorey & Merritt, 2017;Jandausch et al, 2018a), and with mesal edges curved inwards in Symphrasinae) (Ardila-Camacho et al, 2021). The specific shape of the stylets is apparently correlated with the specific larval feeding habits (e.g., Aspöck, 1993;Zimmermann et al, 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, 2006;Wedmann et al, 2013;Komatsu, 2014).…”

“…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).…”