Abstract
Detailed description and illustrations of immature Trictenotoma Gray, 1832 (Trictenotomidae Blanchard, 1845) are presented for the first time, based on larvae and pupae of T. formosana Kriesche, 1919. Characters exhibited by the mature larva are similar to those described by Gahan (1908) for T. childreni Gray, 1832, which was based on a single specimen. The phylogenetic position of Trictenotomidae has varied among Scarabaeoidea, Chrysomeloidea and Tenebrionoidea, though recent studies place the family clearly among the latter. Features of the immature stages described here corroborate this placement. Evidence supports placement within or near the “salpingid group” (Pythidae, Salpingidae, Boridae, Pyrochroidae). Distinguishing features of the mature trictenotomid larva include the absence of stemmata, antennal sensorium, urogomphal pit(s) and lip, the presence of paired series of longitudinal ridges on the meso- and metathorax and abdominal tergites 1–8 and sternites 2–8, a paired arcuate row of 12–15 asperities on the anterior margin of sternite 9 and relatively short, upturned urogomphi. The systematic position of trictenotomids within the Tenebrionoidea Latreille, 1802 is confirmed. The phylogenetic relationships among Trictenotomidae and other “salpingid group” members (e.g., Pythidae Solier, 1834 and Salpingidae Leach, 1815) are highlighted and discussed, solving an almost two centuries old puzzle in Coleoptera systematics.
Highlights
Trictenotomidae Blanchard, 1845 is a small family of Coleoptera Linnaeus, 1758 with two extant genera (Trictenotoma Gray, 1832 and Autocrates Thomson, 1860) with 10 and 5 species, respectively (Gebien 1911; Telnov 1999; Drumont 2006, 2016; Drumont & Telnov 2009)
Stemmata are absent from the head of the last-instar larva (Fig. 27)
The stemmatal configuration seen in the first-instar larva of T. formosana resembles that of the mature larva in many taxa within the “salpingid group” (e.g., most Salpingidae, eurypine and hemipepline Mycteridae, Pythidae, Pyrochroinae and Boridae (Boros Herbst, 1797)) (Young 1991a, 1991b, 1991c, 1991d; Pollock 1991; Pollock & Lawrence 1995)
Summary
Trictenotomidae Blanchard, 1845 is a small family of Coleoptera Linnaeus, 1758 with two extant genera (Trictenotoma Gray, 1832 and Autocrates Thomson, 1860) with 10 and 5 species, respectively (Gebien 1911; Telnov 1999; Drumont 2006, 2016; Drumont & Telnov 2009). The first described taxa of Trictenotomidae were initially placed in two different families of two different superfamilies based on the external morphology of adults: Lucanidae Latreille, 1804 of Scarabaeoidea Latreille, 1802 (Trictenotoma childreni Gray, 1832, type species of Trictenotoma) (Gray 1832) and Cerambycidae Latreille, 1802 (or “Longicornes”) of Chrysomeloidea Latreille, 1802 (Autocrates aeneus (Westwood, 1846), type species of Autocrates) (Westwood 1848) By their appearance – large body, enlarged male mandibles, spinose lateral pronotal margins and threesegmented apical antennal club – these enigmatic beetles resemble lucanids or Prioninae Latreille, 1802 (Cerambycidae) which has led to confusion by earlier authors. Recent analyses, based either on morphological (e.g., Lameere 1916; Crowson 1955, 1981; Watt 1987; Pollock 1994) or molecular (Kergoat et al 2014; McKenna et al 2015; Batelka et al 2016; Zhang et al 2018) characters of adults and larvae (based on the only description of a larval trictenotomid, that of Gahan 1908) have confirmed this tenebrionoid placement and have disproved the earlier placements in Lucanidae or Cerambycidae
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