Ardella magnaemirabilis Paulsen, 2021

Paulsen, M. J., 2021, Ardella magnaemirabilis (Coleoptera: Scarabaeidae: Melolonthinae: Ardellini), a new scarabaeoid species, genus and tribe from the southwestern United States, Insecta Mundi 2021 (903), pp. 1-5 : 3-5

Ardella magnaemirabilis Paulsen , new species

Type material. Holotype male ( TAMU; Fig. 1–4 ) labeled ( Fig. 3 ): a) “ TEXAS: Brewster Co. 1,960 ft. / BBNP, Rio Grande overlook / 1.5 mi. NW R. Grande Village / 29°12′06″N, 102°58′30″W / IV-25-2004, E. Riley-36. UV”; b) on red paper, “ Ardella / magnaemirabilis ♂ / Paulsen / HOLOTYPE ”. Twelve paratype males (7 TAMU, 2 CMNC, 2 UNSM, 1 FSCA) labeled: a) as holotype, but four specimens with abbreviation “TEX”. Three paratype males (2 TAMU, 1 UNSM) labeled: a) “ TEXAS: Brewster Co. / Big Bend National Park , Rio / Grande nr. Boquillas, 1890 ft / 29°11′45″N, 102º55′55″W / 28-IV-2001, MV light trap / Coll. D.E. Baumgardner ”. All paratype specimens labeled: on yellow paper, “ Ardella / magnaemirabilis ♂ / Paulsen / PARATYPE ” . Paratype specimens sent or used for molecular analyses, SEM imaging, and dissection ( CMNC, FSCA, UNSM, respectively) of such an extremely small taxon are considered to have been destructively sampled and may no longer be extant.

Description. Holotype male ( Fig. 1–4 ). Due to monotypy, the generic description above is entirely applicable to the species description, with these additional characters of the holotype specimen. Length: 3.0 mm. Width: 1.2 mm. Color: Dorsum light reddish-brown, pronotum appearing lighter than elytra; abdomen except pygidial disc dark brown. The holotype specimen is missing left protarsomeres 2–5 and right metatarsomeres 4–5.

Description. Paratype males (n = 15) differ from the holotype as follows. Length: 2.6–3.1 mm. Width: 1.1–1.3 mm. Elytra: Except for the incomplete sutural stria, the striae-like longitudinal rugae may be artifacts of desiccation because they do not occur at the same location in all specimens. Some specimens have the abdomen more or less unicolorous with the dorsum, as opposed to that of the holotype which is much darker.

Remarks. As with some other taxa from arid regions, presumably the metatarsi are folded up above the adjacent spurs into a dorsal groove and the corbels of the metatibial apices are used for locomotion, which may also be related to the metatibial spurs not reaching past the apices.

Etymology. The specific epithet, a feminine adjective in the nominative singular, is formed from the Latin words for ‘great’ and ‘wonderful’, which is an ironic nod to such a small insect. It is inspired by the moniker “The Great and Wonderful Ardell” that my sister often humorously insisted that our nieces and nephews call her. An incredibly unique insect can be great no matter the size, and unquestionably it can inspire wonder.

Distribution. The species is known from a single location in the Big Bend area of west Texas.

Discussion. From the comparisons above, and the recent work on Nearctic melolonthine tribes by Evans and Smith (2020), it is clear that this new taxon does not belong in any currently established tribe. For this reason, I propose Ardellini Paulsen , new tribe, with the type genus Ardella Paulsen , new genus, within the subfamily Melolonthinae . It is composed of a single monotypic genus, the generic description above pertaining equally to the tribe. The tribe Ardellini can be diagnosed by the characters listed under the generic description, including the unusual subcircular clypeus, elongate antennal club of males, absence of labrum/mandibles and protibial spurs, cleft protarsal and mesotarsal claws, apparently simple metatarsal claws, and, based on the only known species, its diminutive size of ~ 3mm. The new tribe is composed solely of the monotypic genus Ardella Paulsen , new genus, described herein.

Figures

Figures 1–9. Ardella magnaemirabilis Paulsen, new species. 1–4) Holotype male. 1) Dorsal view. 2) Lateral view. 3) Labels. 4) Ventral view of head and pronotum. 5–9) Paratype male. 5) Dorsal view of head and pronotum. 6) Oblique view of male genitalia.7) Cleft protarsal (left) and metatarsal (right) claws. 8) Dorsal view of right metatibia and metatarsus showing spurs not reaching past tibial apex and simple claws. 9) Right wing, dorsal view.