Morphology of larvae and pupae of the genus Autocrates (Coleoptera: Trictenotomidae) and its phylogenetic implications

Abstract: The trictenotomid genus Autocrates Thomson, 1860 is remarkable for its large and robust adults, but its larval morphology and bionomics have been unknown over the last 160 years. Here, we describe and illustrate in detail the eggs, and also the first and last instar larva and the pupa of Autocrates maqueti Drumont, 2006, based on specimens reared from identified adults collected in South Korea. The first instar larva is very similar to the known trictenotomid larvae of the genus Trictenotoma Gray, 1832, sharing the following features: distinctly flattened and parallel-sided, well-sclerotized head and largely unpigmented postcephalic body, lyre-shaped frontal arms, very short coronal suture, five pairs of stemmata, asymmetrical and tridentate mandibles with mola, simple and apically upturned urogomphi, and absence of longitudinal ridges on the thorax and abdomen. Differences occur in the primary chaetotaxy. The last instar larva is almost identical with Trictenotoma in general appearance, but the longitudinal tergal ridges of Autocrates are much denser and more widely distributed than those of Trictenotoma. Our preliminary assessment of features of immature stages confirms a close relationship of Trictenotomidae with the “salpingid group”, i.e. Salpingidae, Boridae, Pyrochroidae and Pythidae. A sister group relationship with Pythidae is likely. The putative synapomorphy is the subdivision of the ventral element of tergites IX, even though this condition is not visible in the first instars of Autocrates, and quite indistinct (but recognizable) in the last larval stage. The complete mitochondrial genome of A. maqueti is provided. A preliminary phylogenetic analysis of trictenotomid species is presented using two mitochondrial genes (16S and COI). The morphology of eggs and biological information on feeding and oviposition behaviors are also provided with photographs of adults and eggs.

Key words: Coleoptera, Tenebrionoidea, Trictenotoma, chaetotaxy, egg, immature stages, larva, morphology, phylogeny, Korea, Palaearctic Region