Homaeotarsus Hochhuth, 1851

Brunke, Adam J. & Schnepp, Kyle E., 2021, Taxonomic Changes in Nearctic Paederinae, New Records and a Redescription of the Enigmatic Genus Acrostilicus Hubbard (Coleoptera: Staphylinidae), The Coleopterists Bulletin 75 (4), pp. 883-894 : 890-891

Homaeotarsus Hochhuth, 1851

( Figs. 3D–F )

Homaeotarsus Hochhuth 1851: 34 .

Hesperobium Casey 1886. Newton et al. 2000 (as subgenus).

Gastrolobium Casey 1905 . Newton et al. 2000 (as subgenus).

Lissobiops Casey 1905 . Newton et al. 2000 (as valid genus). New synonym.

Diagnosis. Homaeotarsus can be recognized among other New World genera of Cryptobiina by the combination of: thin epipleural line (at least fragment) on the lateral deflexed part of the elytron; a distinct neck that is more than 1/4 as wide as head; and separate (though sometimes narrowly) gular sutures.

Comments. Casey (1905) described Lissobiops for the charismatic and uncommon species Lissobiops serpentinus (LeConte) and distinguished it from Homaeotarsus (then as genera Gastrolobium and Hesperobium) by the incomplete epipleural line on the elytron, the incomplete lateral bead (lateral marginal line) of the pronotum, the narrow neck and unique coloration. Several times, Casey (1905) re- marked on the similarity of Lissobiops with Hesperobium (today a subgenus of Homaeotarsus ) in general and specifically with species Homaeotarsus cribratus (LeConte) and Homaeotarsus rubripennis (Casey) . He even went as far to suggest that, perhaps, Lissobiops could be treated as a subgenus of Hesperobium, with Ho. cribratus and Ho. rubripennis included. It should be mentioned here that Blackwelder’s (1939) separation of Lissobiops from Homaeotarsus based on the sparsely punctate forebody without microsculpture is erroneous, as the abovementioned Homaeotarsus species also have these features.

This group of three species is distinctive among North American Cryptobiina for the nearly or entirely obsolete hind angles of the head and the slightly to distinctly fusiform pronotum.Although it lacks the sparse punctation of the others, Homaeotarsus sellatus (LeConte) also has obsolete hind angles of the head and a similar pronotum shape (contra Casey’s 1905 key) ( Fig. 3D ). With these four taxa, there appears to be a transition from a more typical Homaeotarsus (Hesperobium) [e.g., Homaeotarsus cinctus (Say) ], with distinct hind angles of the head, parallel-sided pronotum, and dense head punctation, to Ho. sellatus ( Fig. 3D ), with obsolete hind angles of the head and a fusiform pronotum, but dense head punctation, to Ho. cribratus / Ho. rubripennis ( Fig. 3E ) with obsolete hind angles, a fusiform pronotum and sparse head punctation. Finally, L. serpentinus ( Fig. 3F ) has the character states of the previous pair of species but with much longer appendages and the epipleural line and pronotal bead variably but always somehow incomplete. The reduction of these lines is probably related to the pronotum and head being unusually convex in Lissobiops . The interruption in the pronotal lateral bead in L. serpentinus is especially variable with some specimens examined bearing only a short interruption. The epipleural line of the elytron is always visible as a fragment but sometimes exists as only a short line, about 3–4 puncture diameters long. While the color pattern of Lissobiops is unique among all North American Cryptobiina, some examined individuals of H. cribratus even have a similar, albeit less contrasting, bicolored red and black head.

Therefore, we propose to treat these four taxa as a distinctive species group ( “ cribratus group”) within Homaeotarsus (Hesperobium) , with Lissobiops as a junior synonym of Hesperobium. The available published CO1 barcode data (www.boldsystems. org, accessed 15 July 2021), visualized using a neighbor-joining tree, the BOLD aligner, and Kimura-2 parameter distances, provide some preliminary corroborating evidence for this group. Homaeotarsus cribratus and H. sellatus cluster together (~8% different) within a larger cluster of other species treated by Casey (1905) as Hesperobium (e.g., Ho. cinctus ). All these taxa form a greater cluster that contains all sampled members of North American Homaeotarsus . Barcode data for Homaeotarsus serpentinus (LeConte) , new combination were not available. It is worth noting that Eucryptina Casey , another genus described by Casey (1905) and also distinguished by the incomplete epipleural line, has long been treated as a synonym of Homaeotarsus , beginning with Blackwelder (1939).

Figures

Fig. 3. Paederinae. A) Stamnoderus monstrosus, dorsal head, B) Pseudolathra oregonensis, protibia, ventral protrusion absent, C) Lobrathium grande, protibia, ventral protrusion present, D) Homaeotarsus sellatus, dorsal habitus, E) H. cribratus, dorsal habitus, F) H. serpentinus, dorsal habitus. Scale bars = 0.2 mm (A–C), 1 mm (D–F).