Pentariini

Johnston, M. Andrew, Naczi, Robert F. C. & Gimmel, Matthew L., 2024, Review of North American Scraptiidae (Coleoptera: Tenebrionoidea), with a Catalog of World Genera, The Coleopterists Bulletin 78 (2), pp. 171-200 : 178-183

Tribe Pentariini

Pentariini Franciscolo, 1954 are readily recognized among Anaspidinae by having the penultimate (fourth) pro- and mesotarsomeres not reduced but distinct and lobed beneath. The genera in this tribe were historically treated along with Anaspidini until Franciscolo (1964) separated the two tribes; he later provided a key to world genera ( Franciscolo 1972). The first genus of this tribe for North America was described as Anthobates LeConte, 1850 to accommodate the species Anaspis trifasciata Melsheimer, 1845 ( Fig. 5 ). Lacordaire (1859: 613) synonymized this genus with Anaspis , claiming that LeConte had committed an error of observation. The next treatment of the type species, A. trifasciata , was by LeConte (1862: 44), who treated it as part of Pentaria Mulsant, 1856 . This latter genus was erected for a single European species; the genus was recognized as valid by Lacordaire (1859: 614), though he had never seen any specimens. North American workers continued to use Pentaria for several decades ( Champion 1890; Smith 1882). Anthobates was mentioned by LeConte and Horn (1883: 408) who claimed it was separated “under false characters, so the name should be rejected, and the more recent one adopted”. However, this is not a valid argument per the principle of priority ( ICZN 1999: Article 23). Accordingly, Liljeblad (1918) recognized the older name and again used Anthobates as valid for this genus and described several new species. Nomenclatural complications were further clarified by Strand (1929: 128; see also Mequignon 1937: 277), who recognized that Anthobates LeConte, 1850 was a junior homonym of Anthobates Gistel, 1848 ( Coleoptera : Curculionidae ) and therefore proposed the replacement name Anthobatula Strand, 1929 . This replacement name is, of course, younger than Pentaria and as such is not presently used. Both LeConte and Horn (1883: 408) and Liljeblad (1918: 154) incorrectly stated that Anthobates and Pentaria share a type species (i.e., A. trifasciata ), but the type species of Pentaria is the Palearctic Anaspis sericaria Mulsant, 1856 by original monotypy. As discussed below, generic limits in Pentariini are in flux, and if future taxonomic splitting of the currently widespread Pentaria is required, the identities of the type species of Anthobatula and Pentaria will be critical.

Arnett (1983) compiled a checklist of North American scraptiids, which he included as the subfamilies Scraptiinae and Anaspidinae within Melandryidae .This checklist was largely a summary of the Leng (1920) and Blackwelder (1945) checklists but also apparently included new distributional data compiled by him, likely from his own collections work. Arnett (1983: 7) newly listed three species described from Mexico as occurring in the United States: Pentaria bicincta Champion, 1890 from Arizona and Texas ( Fig. 6 ), Pentaria brunneipennis Champion, 1890 from Texas, and Pentaria decolor Champion, 1891 from Texas. Unfortunately, he overlooked the fact that a separate genus previously had been erected for P. bicincta which would make this a new country record for that genus. The genus Rhabdanaspis Franciscolo, 1972 (= Rhabdocnemis Franciscolo, 1956 ) was described for P. bicincta based on what was considered a unique pattern of spiculate sculpturing on the mesotibiae, and secondarily by maxillary palpomere 4 without a digitiform sensillum subapically and a subquadrate labrum ( Franciscolo 1956b). Rhabdanaspis has remained monotypic to the present day.

We examined meso- and metatibiae of a number of species of Diclidia LeConte, 1862 and Pentaria , as well as Rhabdanaspis bicincta ( Champion, 1890) , for the diversity of spiculate sculpturing cited by Franciscolo (1956b, 1972). Franciscolo’s (1972) key indicated that Diclidia lacks any such sculpturing; however, the type species, Diclidia laetula ( LeConte, 1858) , clearly possesses two parallel longitudinal spiculate lines on both the meso- and metatibiae, lacks the digitiform sensillum on the apical maxillary palpomere, and possesses a subquadrate labrum (though this character seems to be species-specific as it varies across Diclidia ). The oblique spiculate sculpturing purporting to diagnose Rhabdanaspis was also found in the species Diclidia sordida Liljeblad, 1945 and Diclidia sexmaculata Liljeblad, 1945 . Further investigation showed that P. bicincta is conspecific with D. sexmaculata , and the latter is here proposed as a new junior synonym. As a consequence, Rhabdanaspis is here considered a new junior synonym of Diclidia , resulting in Diclidia bicincta ( Champion, 1890) , new combination. Champion (1890: 254) also indicated that P. bicincta had longer antennae, which historically was the primary diagnostic character of Diclidia in relation to Pentaria . The tibial armature is variable among Diclidia species but seems to be consistent within each species. While the meso- and metatibial spiculate sculpturing does not uniquely identify species, it can be especially useful for identification of female and non-dissected individuals of otherwise externally similar species. It is unclear how many specimens, if any, Franciscolo (1972) had available since his key does not work for most of the described species of Diclidia , including the type species.

Pentaria and Diclidia are very similar and have historically been separated by the relative length of the antennae ( Ermisch 1950a; Liljeblad 1945; Pollock 2002). We comprehensively surveyed the antennomere proportions across all available species of Diclidia and Pentaria . Diclidia generally possess proportionally longer antennae, most easily assessed through examination of the relative lengths of the second and third antennomeres. However, overlap was observed between species of Diclidia with the shortest antennae and typical members of Pentaria . Furthermore, several species displayed significant intraspecific variation of these relative antennomere lengths. Some workers have reported the mesoventrite to be diagnostically compressed and keel-like in Diclidia ( LeConte 1862; Liljeblad 1945), but this state is also observed in most or all Pentaria . Unfortunately, this character state is not observable in most pinned specimens without relaxation, as the procoxae typically lie alongside this median keel. In contrast to the above two characters, detailed examination of the mouthparts revealed two apparently stable, covariate characters: the apex of the mandibles and the presence or absence of a digitiform sensillum near the apical angle of the terminal maxillary palpomere. We found that Pentaria trifasciata ( Melsheimer, 1845) and closely related species from the New World possess bifid mandibular apices ( Fig. 7A ) and a digitiform sensillum subapically on the terminal maxillary palpomere ( Fig. 7B ), while D. laetula and related species (including Rhabdanaspis ) possess entire mandibular apices and no such sensillum on the terminal maxillary palpomere ( Fig. 7C ), although the palpomere often has a narrow, hook-shaped apex.

In a worldwide context, it seems that North American Pentaria and Diclidia violate multiple generic concepts based on such diagnoses as protibia with a longitudinal spiculate ridge (presumably diagnostic of Ectasiocnemis Franciscolo, 1956 but also present in P. trifasciata ) and mesotibial spiculate armature (its presence being the character supposedly separating Pentaria and two other genera from Diclidia and three related genera, though see the discussion above) ( Franciscolo 1972). In light of our morphological analysis, we diagnose Diclidia from North American Pentaria as having the mandibles entire (bifid in Pentaria ) and the terminal maxillary palpomere ending in a slightly hooked tip without a digitiform sensillum (with a preapical, digitiform sensillum in Pentaria ). This new definition necessitates several transfers from Pentaria to Diclidia , discussed below. The remaining North American Pentaria tentatively remain congeneric with European species (see Franciscolo 1972) but need to be evaluated in a worldwide context. Ray (1936) described two species from the Philippines that he placed in Diclidia , but noted that their antennae were short, with antennomeres 3 + 4 together equal to the length of 2. These are the only Diclidia species described from outside of North America and are almost certainly misplaced.

The remaining species of North American Pentaria proved difficult for us to separate. Pentaria trifasciata ( Fig. 5 ) has historically been diagnosed by its trifasciate elytra. However, dorsal coloration presents a continuum of variation. We have seen specimens in which the head and pronotum are nearly completely infuscate ( Fig. 5A ) to those with the head and pronotum entirely testaceous. Often, such variation is present within series from the same collection events. For specimens with a testaceous head and pronotum, there seems to be a spectrum from the three dark fascia occupying most of the elytral disc, to specimens of the unifasciate subspecies Pentaria trifasciata nubila ( LeConte, 1859) ( Figs. 5B, C ), to being entirely testaceous dorsally as in the species referred to by authors as Pentaria pallida ( Liljeblad, 1918) ( Fig. 5D ). Furthermore, we have seen intergrades between the tri- and unifasciate forms. Based on this color variation in combination with morphological homogeneity of these forms, we hereby propose P. t. nubila and Pentaria hirsuta Smith, 1882 as new junior synonyms of P. trifasciata . The syntypes of Pentaria decolor Champion, 1890 represented a mixed series of Pentaria and Diclidia . We here designate a lectotype of specimen NHMUK 015009793 from northern Sonora, Mexico and propose the species as a new junior synonym of P. trifasciata ; it rep- resents the pale form which has often been identified as P. pallida in collections, but see below.All specimens of Pentaria seen by us possess a pair of spiculate longitudinal lines on the mesotibia, though some specimens have a spiculate longitudinal line on the protibia and some do not; this character was not correlated with sex or color pattern. No male genitalic differences were noted in the several dissections performed within this group. We have not seen specimens assignable to other described species of North American Pentaria but we suspect that additional synonyms may be required once all type specimens and additional material are examined.

Naucles has traditionally been separated from the two genera discussed above based on extremely reduced antennomeres and the elytral strigae confined to the basal half. Additionally, the metatibia in Naucles is short and triangular, distinctly shorter than the metafemur and shorter than metatarsomeres 1–2 combined. These characters are here considered to be satisfactory for diagnosing Naucles , but we have not seen Central American and West Indian species to determine how distinct the broader generic concept might be. Franciscolo (1972) provided a key and illustrations for all species of Naucles .

In our work to differentiate genera of Pentariini , we examined hundreds of specimens of Diclidia and many of the primary types.As with Pentaria above, we found cuticle color to be a poor species-level character often showing strong intraspecific variation, even among specimens from the same collecting event, yet this character was the basis for nearly all species concepts before this study. Tibial sculpture, as discussed above, in combination with the shape of the accessory lobes of the male genitalia, were found to be reliable in separating species. A brief account of synonymies and their rationale are presented below.

Diclidia bicincta ( Fig. 6 ) was found to be conspecific with D. sexmaculata , Diclidia propinqua Liljeblad, 1918 , and Diclidia gilva Liljeblad, 1922 , which are all proposed as new junior synonyms. This species tends to be testaceous with either three infuscate bands across the elytra ( Fig. 6B ) or with those bands somewhat broken into three pairs of infuscate spots ( Fig. 6A ). Specimens with the elytra nearly entirely infuscate ( Fig. 6C ) to nearly entirely testaceous have also been seen. The species is characterized by the irregular, sinuous lines of spicules on the mesotibia and the male terminalia ( Figs. 8A–C ) having short, nearly cylindrical accessory lobes adorned with several long setae apically.

Diclidia fuscula ( LeConte, 1862) , new combination was found to be highly variable in dorsal coloration, ranging from dark brown or entirely infuscate to bicolored with testaceous elytra, to entirely flavo-testaceous ( Fig. 9 ). This color variation may be partially linked to distribution, where paler forms are more abundant in arid localities, while darker forms are more prevalent in localities with cooler climates. However, single collecting events can contain both dark and bicolored individuals (e.g., Figs. 9A, B ), while pale and moderately infuscate individuals co-occur as well ( Fig. 9D ). A very weak trend of males being paler in coloration was observed for populations in Arizona, but that was not found to be a reliable way to sex individuals. This species can be easily recognized by the mesotibia lacking spiculate armature and possessing only scattered, isolated black setae and by the male genitalia with the accessory lobes widened apically into a rounded, paddle-like shape with short, stout setae apically ( Figs. 8D–F ). Investigation of types for these characters results in Anthobates bicolor Liljeblad, 1918 , Anthobates pallidus Liljeblad, 1918 , and Diclidia inyoensis Liljeblad, 1922 being proposed as new junior synonyms of D. fuscula .

Diclidia laetula ( Figs. 10A, B ), the type species described from Texas, was found to be conspecific with Diclidia greeni Liljeblad, 1918 , new synonym. The typical color form is testaceous with the elytra bearing an infuscate scutellar cloud and two transverse bands. This coloration can be reduced to paired spots ( Fig. 10B ) or completely testaceous. The species can be recognized by having paired longitudinal lines of spicules on the mesotibia and by the males having a short medial spine on the metafemur ( Fig. 11A ) and the accessory lobes widest at apex, elongate-triangular, with the apex transversely truncate ( Fig. 11I ). Liljeblad (1945) reported D. greeni from Arizona and D. laetula from California, but these were likely based on misidentifications since we did not observe any specimens from those states despite ample material; we consider these state records doubtful until such specimens can be confirmed as D. laetula .

Diclidia obscura Liljeblad, 1945 ( Fig. 10C ), Diclidia sordida Liljeblad, 1945 ( Fig. 10D ), and Diclidia spinea Liljeblad, 1945 ( Figs. 10E, F ) display similar intraspecific variation in color as discussed in the species above. They can be readily identified by the key presented below based on the mesotibial and metafemoral armature and by the shape of the accessory lobes of the male genitalia. Female specimens are often difficult to identify to species unless they are collected in a series with males. We have not examined types of Diclidia species occurring south of the United States, but many of the species that occur along the US-Mexico bor- der likely extend their distributions much further south. It also seems likely that the Chilean Diclidiodes Solervicens, 2016 may belong in our expanded concept of Diclidia , though we have not examined specimens from South America.

Figures

Fig. 5. Pentaria trifasciata, dorsal habitus variation, all scale bars = 1 mm. A) Typical coloration, Utah, B) Darker “nubila” coloration, Utah, same collection event as individual in A, C) Lighter “nubila” coloration, central Arizona, D) Pale form, often referred to as “P. decolor”, southern Arizona.

Fig. 6. Diclidia bicincta, dorsal habitus variation, all scale bars = 1 mm. A) Typical “sexmaculata” coloration, southern Arizona, B) Typical “bicincta” coloration, western Texas, C) Darker form, central Arizona.

Fig. 7. Pentariini, mouthparts. A) Pentaria trifasciata, mandibles, arrow indicating bifid apex, B) P. trifasciata, maxillary palpomere, arrow showing articulated digitiform sensillum, C) Diclidia laetula, mouthparts, arrows indicating entire mandibular apices and lack of digitiform sensillum.

Fig. 8. Diclidia, male abdominal and genitalic morphology. A) D. bicincta, abdomen with extruded male genitalia, B) D. bicincta, apical portion of male genitalia, C) D. bicincta, dissected and cleared male genitalia, D) D. fuscula, dissected and cleared male genitalia, E) D. fuscula, abdominal apex and extruded genitalia in dried specimen, lateral view, F) D. fuscula, same in ventral view. III–VII = abdominal sclerites; al = accessory lobe, articulated processes of fused parameres; bp = basal piece of tegmen; fp = fused parameres of tegmen; p = penis; sp = spicular plates, distal enlarged portions of spiculum gastrale.

Fig. 9. Diclidia fuscula, dorsal habitus variation, all scale bars = 1 mm. A) Typical “fuscula” coloration, New Mexico, B) Typical “bicolor” coloration, Utah, C) Testaceous coloration, Arizona, D) Pale coloration, Arizona, E) Pair in copula showing size and color variation, Arizona.

Fig. 10. Diclidia species, dorsal habitus, all scale bars = 1 mm. A) D. laetula, typical coloration, B) D. laetula, reduced patterning, C) D. obscura, typical coloration, D) D. sordida, typical coloration, E) D. spinea, typical coloration, F) D. spinea, darker coloration.

Fig. 11. Diclidia, diagnostic characters. A) D. laetula, male left metafemur, arrow indicating medial spine, B) D. obscura, male left metafemur, arrow indicating rounded apical spine/projection, C) D. bicincta, mesotibia, dorsal aspect, showing confused oblique lines of spicules, D) D. spinea, mesotibia, dorsal aspect, showing parallel lines of spicules, E) D. spinea, male left metafemur, arrow indicating medial spine, F) D. sordida, male left metafemur, showing unmodified mesal and apical regions, G) D. fuscula, mesotibia, dorsal aspect, showing absence of lines of spicules, only scattered longer dark setae, H) D. obscura, mesotibia, dorsal aspect, showing confused oblique lines of spicules, I) D. laetula, male terminalia, ventral view, J) D. spinea, male terminalia, ventral view, K) D. sordida, male terminalia, ventral view of apex of accessory lobes of parameres, L) D. obscura, male terminalia, dorsal view.