Revision and phylogenetic analysis of the genus Acanthischium Amyot & Serville, 1843 (Hemiptera: Reduviidae: Harpactorinae)

The Neotropical harpactorine assassin bug genus Acanthischium Amyot & Serville, 1843 (Hemiptera: Reduviidae: Harpactorini) includes four valid species: Acanthischium maculatum Amyot & Serville, 1843 (with ten color varieties proposed by Stål [1872]), Acanthischium haglundi Stål, 1866, Acanthischium superbum Haviland, 1931, and Acanthischium invium Elkins, 1961. A taxonomic revision and a morphological phylogenetic analysis were carried out to test species limits and to propose a hypothesis of evolutionary relationships. As a result of the phylogenetic analysis, Acanthischium is characterized on its external morphology by the elongate postocular region, posterior margin of the pronotum with spines, ventral surface of protrochanter with apical and basal protuberances, profemur wider than mesofemur, and protibia strongly curved. After the taxonomic revision we propose nine valid species, taking into consideration characters of external morphology, male and female genitalia, and color patterns: Acanthischium dimidiatum Stål, 1859 stat. rev.; Acanthischium flaviceps Stål, 1872 stat. rev.; Acanthischium haglundi Stål, 1866; Acanthischium kuna sp. nov. from Panama and Colombia; Acanthischium maculatum Amyot & Serville, 1843; Acanthischium meloae sp. nov. from Suriname; Acanthischium nigrum Stål, 1872 stat. rev.; Acanthischium semiflavum Stål,1872 stat. rev.; and Acanthischium superbum Haviland, 1931. We further synonymize A. invium Elkins, 1961 with A. superbum. All but one of the species ‒ A. flaviceps ‒ were included in the phylogenetic analysis, in which Acanthischium was found to be monophyletic, with the following set of relationships: (A. haglundi + (A. nigrum +(A. dimidiatum (A. maculatum, A. semiflavum, A. kuna, A. meloae, A. superbum)))). The resulting phylogenetic pattern indicate a body color transition from drab to more vivid ones, such as orange or red. The species exhibiting red and orange colorations are found in a clade, suggesting an underlying biological phenomenon, such as wasp mimetism.