Doyenellus, Nabozhenko & Steiner, 2021

Doyenellus, Nabozhenko & Steiner, 2021

Nabozhenko & Steiner (2021) described a new genus based on three flightless species from the southeastern United States: Doyenellus cisteloides (Germar) ; and two new species, Doyenellus worthleyorum (Steiner) and Doyenellus theodorei (Steiner & Nabozhenko) . Doyenellus is the only recently and comprehensively circumscribed genus of New World Helopina which allows for a more detailed examination of putatively diagnostic character states than the rest of the genera discussed herein. The following six characters were reported as unique or diagnostic of Doyenellus which are worth further examination.

1. The “eighth elytral interval convex or keel-shaped and connected with elytral margin apically” (Steiner & Nabozhenko 2021: 571).

The eighth elytral interval (with the interval between the elytral fusion and the first stria counting as interval one and counting outward towards the epipleuron) is variably developed among the three species presently placed in Doyenellus and is particularly weakly elevated in D. theodorei ( Fig. 3A View FIGURE 3 ). There is large variation in the general convexity, flatness, and punctation of elytral intervals across Helopina species in North America.A keeled or convex eighth elytral interval is found in a number of species, including Helops rufipes (LeConte) ( Fig. 3F View FIGURE 3 ).

2. Male venter with “elevated male abdominal ventrites 3–4, enlarged intersegmental membranes and strongly convex abdominal ventrite 5 (unique sexual dimorphism within the subtribe Helopina )” ( Nabozhenko & Steiner 2021: 571).

The secondary sexual characters of the male abdomen are quite variable among New World Helopina , especially with regard to the fifth ventrite which is often inflated or depressed and can bear a wide range of setose fields or patches. The reportedly unique structure of the enlarged intersegmental membranes and convex fifth ventrite is also found in other species, including Tarpela micans (Fabricius, 1798) ( Fig. 3B View FIGURE 3 ), likely the most commonly collected species in the eastern United States. Moreover, this character is highly variably developed in the three species originally included in Doyenellus (see figures 13, 15, 17 in Nabozhenko & Steiner 2021: 569). This character is not only not unique among the New World fauna, but the variation seen in other species currently assigned among the genera Tarpela and Helops lead us to believe these characters are best used for species-level diagnoses.

3. Males further characterized by “reduced, delimited and weakly sclerotized auriform apices of male inner sternite VIII (unique character within Helopini )” ( Nabozhenko & Steiner 2021: 571).

As with the external secondary sexual characters discussed above, male sternite VIII displays a large amount of variation across New World Helopina species. In all species examined by us, this sternite is deeply emarginate medially, separating the distal half of the sclerite into a pair of sublateral lobes. These lobes are typically less sclerotized and appear more fleshy than the proximal portion of the sclerite. The lobes range from large and paddle shaped, to narrowly pointed triangles ( Fig. 3E View FIGURE 3 ), and to elongated almost digitate processes. The state defined for Doyenellus is not unique or easily characterized as a discrete state among the rest of the variation in this fauna. Moreover, the “auriform” lobes given as a generic character for Doyenellus are most distinct in D. cisteloides and are quite different in the other two species (see figures 34, 42, 51in Nabozhenko & Steiner 2021). We similarly find this character useful for diagnosing particular species but the variation in the species presently placed in Doyenellus merely reflects some of the variation seen across New World Helopina and is not satisfactory for delimiting a genus.

4. Male penis (or median lobe) “having a dorsally pubescent, narrowly rounded apex and ventral bifurcated bare apex” as opposed to the “typical catomoid median lobe with one widely rounded apex” ( Nabozhenko & Steiner 2021: 571).

This character can be more precisely defined as the margin of the ostium of the penis. The penis of Tenebrionidae is a tube-like structure which is supported by a Y- or wishbone-shaped longitudinal sclerotized portion called the penis rod (Doyen 1966) or median-lobe baculus (Matthews & Bouchard 2008). At the distal end of the penis, between the two forks of the penis rod or baculus, is the ostium, or the opening through which the internal sac is everted during copulation (for definitions and drawings, see Lawrence & Ślipiński 2013 and Doyen 1966). Thus, the character discussed here is reporting that the ostium of Doyenellus is bounded above by a single rounded margin while ventrally it is incised medially. All New World Helopina we have examined have the ostium located apicoventrally where the opening can be difficult to characterize depending on the preservation and state of the internal sac which is often slightly protruding and may obscure the true boundary of the ostium. The ostium of Doyenellus ( Fig. 3C View FIGURE 3 ) is accurately described by Nabozhenko & Steiner (2021) but the variation seen across New World Helopina does not allow for simple attribution of character states across species. For instance, some species have a much more deeply incised ventral margin of the ostium ( Fig. 3D View FIGURE 3 ) while others seem to have a fully bilobed apex of the penis where both the top and bottom are incised ( Fig 3E View FIGURE 3 ). This seems to be an important character system that could diagnose particular species but we see no consistent or easily binary character states which separate phylogenetically distinct genera. The incised ventral margin of the ostium is clearly not unique to Doyenellus .

5. Female genital tube with the “presence of one-way valve (valve without short processes laterally) in base of accessory gland duct (unique character within American Helopini )” ( Nabozhenko & Steiner 2021: 571).

Nabozhenko & Steiner (2021: 572) state that this character is “unusual within American Helopini but not unique within Helopini of the world.” We only examined the internal female genital tube of two species (the robust flightless species Helops opacus LeConte, 1859 from California, and an undescribed narrow flighted species from Arizona which is very consistent with Central American Tarpela ). Both had all the same characteristics as described for Doyenellus and possessed a one-way valve at the base of the accessory gland ( Fig. 3G View FIGURE 3 ). Nabozhenko & Steiner (2021) did not mention how many other New World species they may have examined, but this state is not unique and our limited sampling suggests it is likely common if not ubiquitous.

6. Leg armature characterized by “dilated male pro- and mesotarsi, very long setae around the tibial apex” ( Nabozhenko & Steiner 2021: 571).

This character was included in the structures which putatively diagnose Doyenellus but was not reported as unique to the genus, which it is not. Dilated male tarsi may be more common among flightless species, but we have observed this across all of the other genera currently recognized for North American Helopina .

All six of the character systems presented as diagnostic for Doyenellus are inadequate to readily diagnose a genus among the North American Helopina . The three species currently placed in the genus may be closely related, with D. cisteloides being particularly apomorphic, especially in the secondary sexual characters discussed above, and the two other species presenting, at best, variations on that theme. However, these putatively diagnostic characters were not satisfactorily surveyed across the broader fauna during the original description and they do not serve to adequately diagnose a separate genus.