Ecomorphological diversification of the Late Palaeozoic Palaeodictyopterida reveals different larval strategies and amphibious lifestyle in adults

The Late Palaeozoic insect superorder Palaeodictyopterida exhibits a remarkable disparity of larval ecomorphotypes, enabling these animals to occupy diverse ecological niches. The widely accepted hypothesis presumed that their immature stages only occupied terrestrial habitats, although authors more than a century ago hypothesized they had specializations for amphibious or even aquatic life histories. Here, we show that different species had a disparity of semiaquatic or aquatic specializations in larvae and even the supposed retention of abdominal tracheal gills by some adults. While a majority of mature larvae in Palaeodictyoptera lack unambiguous lateral tracheal gills, some recently discovered early instars had terminal appendages with prominent lateral lamellae like in living damselflies, allowing support in locomotion along with respiratory function. These results demonstrate that some species of Palaeodictyopterida had aquatic or semiaquatic larvae during at least a brief period of their post-embryonic development. The retention of functional gills or gill sockets by adults indicates their amphibious lifestyle and habitats tightly connected with a water environment as is analogously known for some modern Ephemeroptera or Plecoptera. Our study refutes an entirely terrestrial lifestyle for all representatives of the early diverging pterygote group of Palaeodictyopterida, a greatly varied and diverse lineage which probably encompassed many different biologies and life histories.

A new species of Cryptonympha Lugo-Ortiz & McCafferty (Ephemeroptera, Baetidae) from Cerro Duida (Venezuela)

The genus Cryptonympha includes three species: C. copiosa Lugo-Ortiz & McCafferty, 1998; C. dasilvai Salles & Francischetti, 2004 and C. genevievae Thomas, Manchon & Glémet, 2013, known only from the nymphal stage. A description of the nymph of a fourth representative, Cryptonympha tracheata sp. n. is provided here, based on material collected in a blackwater stream on the slopes of the Cerro Duida mountain in south-western Venezuela. The nymph of the new species can be easily distinguished from the other species of the genus by very long tracheal gills II–VII, 2.5 times the length of each tergum, gill I small, nearly half length of gill IV and by posterior margin of terga with rounded spines. A complete description of the new species and a key for nymphs of all known Cryptonympha species are provided.

Larval morphology of Yateberosus, a New Caledonian endemic subgenus of Laccobius (Coleoptera: Hydrophilidae), with notes on ‘Berosus-like’ larvae in Hydrophiloidea

The morphology and head chaetotaxy of the second and third instar larvae of Laccobius (Yateberosus) sp. are described based on specimens collected in New Caledonia. The larvae agree with those of other subgenera of Laccobius Erichson, 1837 in most morphological characters including the morphology of head and mouthparts and the head chaetotaxy, which undoubtedly supports its assignment to Laccobius (Yateberosus). It differs from other Laccobius in the closed spiracular system, reduced spiracular atrium and long abdominal tracheal gills, in which they resemble the larvae of Berosus Leach, 1817. We demonstrate that the ‘Berosus-likeʼ larval morphology evolved at least four times independently in Hydrophiloidea, and briefly discuss the possible reasons for it.

New palaeodictyopterans from the Late Carboniferous of the UK (Insecta: Palaeodictyopterida)

ABSTRACTNew palaeodictyopterans, Vernooijia sassoonae gen. et sp. nov. (Breyeriidae) and Mazonopterumcooperi sp. nov. (Homoiopteridae) are described from the Middle Pennsylvanian (Westphalian D/Late Asturian) of Writhlington, near Radstock (UK). Based on the re-examination of venation in Breyeriaharlemensis, we propose the transfer of this species to the genus Vernooijia as V.harlemensis (Brauckmann & Gröning, 1996) comb. nov. We report the first record of Homaloneura sp. (Spilapteridae) from the Langsettian to Duckmantian of Coseley, Staffordshire. Additionally, we report a fragmentary wing from the Middle Pennsylvanian (late Westphalian D/early Cantabrian) of the Forest of Dean, Gloucestershire, tentatively belonging to the Lycocercidae. Our re-examination of a putative blattodean nymph described by Rolfe (1967) allows re-assignment to Palaeodictyoptera, as it has well-developed wing pads with a corrugated pattern of probably original tracheation and lacunal channels, identified as presumably nymphal exuvia of Idoptilus sp. Surprisingly, our study reveals the presence of three triangular caudal appendages bearing prominent lateral lamellae emerging from the terminal abdominal segment, previously unknown in other nymphs of Palaeodictyoptera. We assume that these lamellae were originally covered with dense setae and possibly represent modified caudal appendages in the form of tracheal gills, as known in the nymphs of damselflies (Odonata: Zygoptera). Thus, the scenario of a possible aquatic lifestyle for nymphs of at least some members of Palaeodictyoptera, as considered by Brongniart (1885, 1893) and Handlirsch (1906), cannot be definitely excluded.

Phylogenetic relationships, larval morphology, and chaetotaxy of the subfamily Coptotominae (Coleoptera: Dytiscidae)

Larval morphology of the monogeneric subfamily Coptotominae (Coleoptera: Dytiscidae) is described and illustrated in detail, with particular emphasis on morphometry and chaetotaxy. Larvae ofCoptotomusSay are unique within Dytiscidae in the presence of tracheal gills on the abdominal segments I–VI, a short bifid horn or nasale in instar I, long spinulae on the urogomphus in instar I, and rows of natatory setae on both the internal and external margins of the urogomphus in instars II and III. A cladistic analysis based on 125 larval characters sampled among representatives of other dytiscid subfamilies supports a sister-group relationship between Coptotominae and Laccophilinae based on the shared absence of setae LA10 and LA12 on the second labial palpomere and of pore ABc on the abdominal segment VIII. The clade Coptotominae + Laccophilinae resolved as sister to Lancetinae, all three subfamilies sharing the presence of an unusually low number of lamellae clypeales in the first instar (a condition called four-peg-pattern), postulated to have evolved secondarily within Dytiscidae.

The external larval morphology of aquatic and terrestrial Luciolinae fireflies (Coleoptera: Lampyridae)

The external morphology of aquatic, semiaquatic and terrestrial lucioline larvae was investigated in order to provide anoverview of what traits constitute the extremely ecologically diverse Luciolinae (Coleoptera: Lampyridae). The aquaticspecies, Aquatica ficta (Olivier), A. leii (Fu et Ballantyne), A. hydrophila (Jeng et al.), A. lateralis (Motschulsky), A. wu-hana Fu et Ballantyne, Luciola cruciata Motschulsky and L. owadai Satô et Kimura cannot swim, but instead crawl onthe substrate. They have soft bodies, lateral abdominal tracheal gills and glands on eversible structures that secrete repel-lent substances. The back-swimming species, Luciola substriata Gorham and L. aquatilis Thancharoen, which inhabit thesurface of ponds, have hardened exoskeletons, and lack gills and eversible glands. Unlike the crawling species, the back-swimmers have sense organs along the ventral surface of the apical maxillary and labial palpomeres, and are metapneusticin their later instars. The larval morphology of the aquatic species is contrasted with Pygoluciola qingyu Fu et Ballantyne, whose larvae are semiaquatic and lack gills, and with the terrestrial larvae of Asymmetricata circumdata (Motsch.) (newly

Some observations on altered morphology in Amphipsyche meridiana (Hydropsychidae: Trichoptera) larvae from the Pasak Jolasit Dam Outlet, central Thailand

Amphipsyche meridiana Ulmer, 1909. larvae from the River Pasak below the Pasak Jolasit Dam were examined for alteration of morphological structure such as the anal papillae, surface, and tracheal gills of the larvae. The tracheal gills were the most altered followed by surface and anal papillae. Factors such as conductivity, and inputs of orthophosphate, sulfate, turbidity, other contaminants, and/or stream profiles may have contributed to the abnormalities.