Description of the late- or last-instar larva of Ischyomius Chevrolat, with comments on the family placement of the genus (Coleoptera: Tenebrionoidea: Pythidae)

Darren A Pollock,Jim Mcclarin

doi:10.11606/1807-0205/2020.60.special-issue.11

Abstract

Study of recently collected larvae of two species of Ischyomius Chevrolat, 1871 from Napo and Pichincha, Ecuador, tentatively identified as I. denticollis Champion, 1916 and I. singularis Chevrolat, 1871 confirm the classification of the genus Ischyomius within the family Pythidae. Salient larval characters which solidify this placement are: 5 stemmata arranged into an anterior column of 3 and posterior column of 2, parabasal ridges along anterior margins of abdominal tergites, prominent urogomphi with inner urogomphal teeth and various dorsal tubercles, and transverse row of dentiform asperities along anterior margin of sternite 9. Important features of the larva are illustrated with photographs. A key to larvae of world genera of Pythidae is provided as well as natural history information on Ischyomius.

Highlights

The Neotropical genus Ischyomius Chevrolat, 1878 currently contains eight species, encompassing a geographical range from Costa Rica in the north, to Bolivia in the south (Pollock, 1998, 2007, 2009)
The larvae of Ischyomius and their morphological features have appeared in the “material examined” sections of a few studies, despite the fact that they had not been formally described
Lawrence et al (2011) used 516 morphological features of both adults and larvae including Ischyomius chevrolati Champion 1916 and Pytho niger Kirby 1837 to elucidate a phylogeny of the entire Coleoptera

Summary

Introduction

The Neotropical genus Ischyomius Chevrolat, 1878 currently contains eight species, encompassing a geographical range from Costa Rica in the north, to Bolivia in the south (Pollock, 1998, 2007, 2009). Placement of Ischyomius in Pythidae was first suggested by Lawrence (1982), who offered no detailed supporting evidence for this placement In their treatment of beetle classification, Lawrence & Newton (1995) placed Ischyomius as Pythidae, incertae sedis. As mentioned by Pollock & Lawrence (1995: 467), “an additional three genera, Ischyomius, Trimitomerus and Osphyoplesius, should be placed there [Pythidae] tentatively, pending more detailed morphological studies and/or the discovery of the immature stages”. This statement was repeated by Pollock (1998), as Ischyomius historically has been somewhat enigmatic taxonomically

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