Larvae of Rhipsideigma raffrayi are described in detail and those of Distocupes varians are re-examined. Their morphological structures are evaluated with respect to their functional and phylogenetic significance. Larvae of Rhipsideigma are wood-borers with a straight body and a wedge-shaped head capsule. Most of their apomorphic features are correlated with their xylobiontic habits. The strong mandibles, the sclerotized ligula and the wedge-shaped head enable the larvae to penetrate rotting wood. The broadened prothorax, prosternal asperities, tergal ampullae, the short legs, and eversible lobes of segment IX play an important role in locomotion in galleries within rotting wood. Leg muscles are weakly developed, whereas the dorsal, pleural and ventral musculature is complex. The larval features allow Rhipsideigma to be placed in the clades Archostemata, Cupedidae + Micromalthidae, Cupedidae, Cupedidae excl. Priacma, and Cupedidae excl. Priacma and Distocupes. The monophyly of Cupedidae and Cupedidae, excluding Priacma, so far is only supported by apomorphies of the adults. However, the presence of glabrous patches on the prosternum and of a medially divided field of asperities may be larval apomorphies of the family. A clade, which comprises Rhipsideigma, Tenomerga and probably other genera of Cupedidae with hitherto unknown larvae, is well supported by larval apomorphies such as the broadened prothorax, the presence of coxal asperities and the presence of a distinct lateral longitudinal bulge. Increased numbers of antennomeres and labial palpomeres are apomorphies only found in larvae of Distocupes.
This paper presents a synthesis of morphological information on larvae of the beetle suborder Archostemata. Larvae of the following families and species were studied: Ommatidae: Omma sp.; Micromalthidae: Micromalthus debilis LeConte, 1878; Cupedidae: Priacma serrata LeConte, 1861, Distocupes varians (Lea, 1902), Rhipsideigma raffrayi (Fairmaire, 1884), Tenomerga cinerea (Say, 1831) and Tenomerga mucida (Chevrolat, 1829). Morphological characters of the suborder and three families are described. Monophyly of the suborder is strongly supported by more than 10 larval autapomorphies. A close relationship between Micromalthidae and Cupedidae is confirmed. New larval characters are introduced, including chaetotaxy of first instar larvae of Micromalthus LeConte, 1878, Priacma LeConte, 1874 and Distocupes Neboiss, 1984. An identification key to families and subfamilies of Archostematan larvae is provided, along with a checklist of extant Archostemata taxa. The work is illustrated with 120 morphological drawings.
Internal and external features of the head of Ascioplaga mimeta (Coleoptera: Archostemata) were studied with micro X-ray computertomography (µCT) and nuclear magnetic resonance imaging (NMRI). These methods allowed the reconstruction of the entire internal anatomy from the only available fixed specimen. The mouthparts and their associated musculature are highly derived in many aspects. Their general configuration corresponds to that of Priacma serrata (the only other archostematan studied in comparable detail). However, the mandible-maxilla system of A. mimeta is built as a complex sorting apparatus and shows a distinct specialisation for a specific, but still unknown, food source. The phylogenetic analysis resulted in the identification of a new monophylum comprising the genera [Distocupes + (Adinolepis +Ascioplaga)]. The members of this taxon are restricted to the Australian zoogeographic region. The most prominent synapomorphies of these three genera are their derived mouthparts.