Phyllophaga (Listrochelus) benwarneri Warner, 2021

Warner, William B., 2021, Two new scarab beetles from the southwestern USA (Coleoptera: Scarabaeidae: Melolonthinae and Aphodiinae), Insecta Mundi 2021 (855), pp. 1-15 : 1-9

Phyllophaga (Listrochelus) benwarneri Warner , new species

Figures 1 , 4 , 5 , 8, 10 , 12–17

Diagnosis. Head lacking carina along basal margin; clypeus medially emarginate. Elytra together very convex, with humeral umbones obsolescent, apical umbones, striae and costae obsolete; metathoracic wings reduced (shorter than elytron) and nonfunctional. Meso- and metatibia slightly shorter than their respective basal three tarsomeres combined; tarsal claws on ventral edge with one row of weak serrulations in about basal half, lacking larger teeth in male, with even weaker serrulations and small median tooth on both claws in female. Female pygidium with fovea at middle of about apical fifth. Male with parameres bilaterally symmetrical, fused into tube with dorsal opening; aedeagus sclerotized, tubular, apex ventrally barbed (“harpoon-like”).

Type data. Holotype male (deposited at ASUT) and allotype female labeled: “ USA: AZ: Mohave Co.; dunes S of Beaver Dam; 36°54′10″, 113°56′33″W, iv.24.1998; B.C. & W.B.Warner, J.Huether; on sand at night.”

Description of holotype male. Length: 11.5 mm; widest width (about apical fourth of elytron): 5.0 mm. Body elongate, reddish-brown, convex. Head and clypeus subcontiguously punctate; clypeus about as long as rest of head with free margin biarcuate and apically moderately reflexed, medial emargination obtusely subangulate. Antennal club about as long as clypeus. Pronotum widest at about middle, about 2⁄5 as long as elytron, slightly wider than elytra at humeri, width about 1.5 times length at midline, anterior margin weakly arcuately emarginate, posterior margin weakly convex and subparallel to anterior margin, lateral margins obtusely subangulately convex, rather remotely serrate in anterior half, fringed with long flying hairs; disc bare, moderately coarsely, but distinctly punctate, punctures mostly separated by about 1–3 times their own widths. Scutellum short and broad, apex arcuate, base about half as wide as base of elytron; disc vaguely, sparsely punctate. Elytron relatively dull (contrasting with that of female), in dorsal view sides more or less straight and weakly diverging to about apical fourth, discal striae obsolete, sutural stria obsolescent, only vaguely indicated by slight impression or color change; disc sparsely weakly punctate, punctures much shallower and only a third or so as large as pronotal punctures, setigerous, setae mostly less than twice as long as diameter of puncture from which they emerge. Pygidium dull and sericeous as in elytron, disc sparsely punctate, punctures fine, shallow. Venter dull as in elytron; thoracic sternites with long but only moderately dense testaceous pile; abdominal ventrites with setae shorter and sparser; apex of penultimate abdominal ventrite medially narrowly and shallowly emarginated; base of apical ventrite medially transversely subtuberculate ( Fig. 7 ). Legs long, profemur fringed on dorsal (anterior in repose) and ventral edges (meso- and metafemora primarily on dorsal edge) with long flying hairs; protibia distinctly tridentate, basal tooth at about middle; meso- and metatibia shorter than their respective basal three tarsomeres together; tarsi long (meso- and metatarsi about 3/4 as long as elytron, basal four protarsomeres ending with short apicoventral mucro, this reduced in mesotarsus and nearly obsolete in metatarsus; tarsal claws with ventral edge weakly serrate in about basal half, lacking larger tooth. Genitalia with parameres ( Fig. 4 ) fused into tube with dorsal opening, in lateral view arcuately narrowing to mucronate apex; aedeagus heavily sclerotized into tube, open dorsally, in lateral view apically weakly deflexed and arcuately narrowing to apex, with dull “harpoon-like” barb emanating from ventral edge and directed posteroventrally.

Female allotype. Length: 14.0 mm; widest width (slightly behind elytral midpoint): 7.0 mm. Similar to male but broader, more rotund, and darker in color than male, widest at about apical third of elytron; elytron oval, smoother, shiny and more convex than in male, appearing “inflated,” with punctures weak to obsolescent; pygidium flatter, with distinct medial fovea at about apical 1/4; tibiae comparatively longer and more robust, protibial teeth stronger, metatibial corbels broader, tarsi less robust and comparatively shorter than in male (metatarsus about 2/3 length of elytron); antennal club about half as long as clypeus. Genitalia: in ventral “in face” view inferior plates obliquely subcordiform, medially tightly abutting but not fully fused, disc irregularly convex, dorsolateral lobe concave; superior plate subhastate, lateral “wings” partially covered by inferior plates, middle half flattened except for vague longitudinal sulcus at each side of middle, lateral fourths angularly moderately deflexed, apical margin weakly emarginated at each side before deflexed portions, margin on deflexed portions weakly convex, with about 5 long erect setae on each.

Paratypes. 419 males, 286 females with data: Same as holotype (8m, 1f); “ Beaver Dam , Mohave Co., AZ, iv-23- 1984, J.P.Davidson, J.M.Davidson ” (2m, 2f) ; same except: “I-15 W side of exit at Beaverdam, iii.21.2003, W.B. & B.C. Warner ” (7f) ; same as holotype except: “Beaverdam; N36°53′40″, W113°56′02″; iv.1.2012, night feeding & mate on Oenothera flowers; W.B.Warner ” (47m, 66f) ; same except: iv.14.2015 (77m, 50f); same except: “G.S.Powell” (17m, 7f); same except: “K.E.Schnepp” (25m, 15f); same except: “ iv-20-2014, feeding on Oenothera deltoides at night; W.B.Warner” (64m, 36f) ; same except: “iv.2-v.18.2012; barrier pitfall / “fake burrow” blk. cups” (20m, 5f) ; same except: “ 1,916 ft., Beaverdam, feeding / mating on flowers + leaves of Oenothera , 36°53′40″N, 113°56′02″W, 1-April-2012, at night, R. A.Cunninghham + W.B.Warner ” (42m, 29f), same except: “ 36°53′41″N, 113°55′55″W, 1-4/April/2012, black cup pitfall traps ” (1m, 1f); same except: “ Beaver Dam nr jct Hwy 15 & Hwy 91, Elev. 2000′ 36 53.703N, 113 56.002W, on Oenothera , 4/5/2013 to 4/7/2013 ; R.H. McPeak ” (38m, 28f); “ USA: AZ ; Mohave Co., 1880 ft., Littlefield Sand Dunes , I-15, 0.2 mi. S. of County Rd. 3454, 36°53′32″N, 113°55′55″W, 26-IV-2003, R. A.Cunningham ” (14m, 4f); “ USA: NV: Clark Co., 0.4 mi. W. jct. of I-15 & Hwy. 169 ; 3640′16″N, 114°31′49″W; May 31, 2012; dune, night; R. A.Cunningham ” (1f); same except: “ April 12, 2015, K.E.Schnepp ” (1m); “ USA: NV: Clark Co., St. Thomas Gap dunes, 36.4100°, -114.0904 °; 30-IV-2018; M.A.Johnston ” (1m, 1f) “ USA: NV: Clark Co., Hwy. 167, nr. Echo Wash bridge, 450m, pitf. in open, DP5 ; 36°18′35″N, 114°29′21″W; 21.iv.2008; Suazo & Ibarra” (1f); USA: NV: Clark Co., Hwy. 167, NE jct. Valley of Fire Hwy. , 465m, pitf. under shrub, GYP1 ; 36°26′24″N, 114°25′36″W; 21.iv.2008; Suazo & Ibarra ” (1m, 1f); same except: “GYP2 ; 36°26′26″N, 114°25′31″W ” (5m); same except: “pitf. in open” (1m, 2f); same except: “GYP3; 36°26′24″N, 114°25′31″W ” (1m, 5f) ; same except: “pitf. under shrub” (19m, 13f); “ USA: NV: Clark Co., Hwy. 167, W jct. Rt. 12; 430m; pitfall in open GYP4; 36°26′17″N, 114°24′46″W; 21.iv.2008; Suazo & Ibarra” (2m, 5f) ; same except: “pitfall under shrub” (8m, 1f); same except: “GYP5; 36°26′17″N, 114°24′43″W ” (19m, 2f) ; same except: “pitfall in open” (6m, 3f).

Specimens are deposited in all of the collections mentioned in the Materials and Methods.

Variation. Males: Length 10.0–13.0 mm, widest width 4.5–6.0 mm. Females: Length 11.0– 15.5 mm, widest width 5.0– 7.5 mm. Variation other than in size primarily in slight body proportion differences. In males, mediobasal area of last abdominal ventrite varying from roughened transverse umbo to more or less distinct tubercle. Female superior genital plate medioapically with shallow and narrow emargination in some specimens; color variable but usually darker than males.

Etymology. I name this species in honor of my son, Benjamin C. Warner, who as an adolescent collected the first specimen of the holotype series as it was sitting on bare sand. He presented it to me, then proceeded to collect five additional specimens, excitedly calling out each capture, while both the frustrated author and fellow frustrated collector Jeff Huether frantically searched the same small area for over 30 minutes before finally finding a few specimens. He continues to frustrate me in such pleasant ways to this day.

Habits and habitat. The holotype series was collected as they sat or walked on bare sand at night on low, uncon-

solidated dunes immediately southwest of Beaverdam, Arizona. Subsequent trips to the area yielded specimens in similar situations, as well as many specimens collected while they fed on sand verbena ( Abronia sp. , Nyctaginaceae ) or much more commonly Oenothera deltoides Torrey and Fremont (Onagraceae) . Two large series collected by the author and R. A. Cunningham on the same dunes a few hundred yards away on April 1, 2012 and April 20, 2014, another by the author, K. E. Schnepp and G. S. Powell on April 14, 2015, as well as another series of 66 taken April 5–7, 2013, by R. H. McPeak, were taken at night nearly entirely while the specimens fed on Oenothera (mostly flowers, but occasionally on bracts or leaves), or were mating on the same plants. Additional specimens were collected in barrier pitfall samples set the day after the 2012 series was collected, as well as in pitfall traps or “headlamping” at night on blow sands in nearby Nevada localities in an arc ending in the Moapa Valley/Valley of Fire area.

Beaverdam is adjacent to Littlefield, Arizona, both small, unincorporated towns located near the confluence of Beaverdam Creek and the Virgin River in the extreme northwestern corner of the state about 13 km northeast of Mesquite, Nevada. The type locality is on the bluff that borders the southwest edge of the Beaverdam Creek flood plain, a riparian area that cuts through the Mojave Desert biotype from which most of the type series was collected (mostly from the rim of the bluff to approximately 300 meters southwest of the rim). Primary perennial plants at the site are Larrea tridentata (de Candolle) Coville , Ambrosia dumosa (A. Gray) Payne and Ephedra species ; scattered Yucca brevifolia Engelmann dot the surrounding desert. The riparian area immediately adjacent to the type locality is dominated by cottonwood ( Populus freemontii S.Watson ), willow ( Salix species ), desert willow ( Chilopsis linearis (Cavanilles) Sweet ), seep willow ( Baccharis glutinosa (Ruiz and Pavón) Persoon ) and desert shrubs, although specimens of P. benwarneri have only been found on the dry blow sands on the bluffs above the flood plain, and in similar habitats to the southwest. Other precinctive scarab beetles known from the same habitats in those locations include the flightless Diplotaxis robertmarki Davidson and Davidson and Aegialia knighti Gordon and Rust , as well as Diplotaxis coenonychoides Davidson and Davidson (which flies and also occurs in a few nearby dunes in southwestern Utah). The same dune system is the type locality of the precinctive meloid beetle Lytta arizonica Selander , and is the habitat of two undescribed Trigonoscuta species ( Curculionidae : Entiminae ; C. W. O’Brien, pers. comm.).

Relationships. Phyllophaga benwarneri is a member of the Phyllophaga (Listrochelus) senex (Horn) lineage, and forms the western-most population of that “superspecies.” The Phyllophaga senex complex species share similar male genital structure, tarsal claws with only weakly serrate ventral edge, and female pygidial fovea. Both sexes of P. benwarneri , however, are flightless, differ in surface sculpture, have much hairier legs, a distinctly biarcuate clypeal margin, and more strongly developed pronotal marginal beading than other members of the senex complex. Females of P. benwarneri may be distinguished from those of other taxa in the P. senex complex by their more strongly basally constricted pronotum and elytra, longer legs, wider head with larger, more prominent labrum and longer clypeus, nearly semicircular (vs. triangular) scutellum, elytron with flat sutural interval, and smoother, more finely punctate dorsum (e.g. compare Fig. 8 and 9 ).

Additionally, P. benwarneri is ecologically, altitudinally and geographically isolated from nearest known populations of other senex complex phenotypes by several mountain ranges and the Colorado and Virgin Rivers (including the Grand Canyon). Interestingly, this pattern follows a similar situation with Diplotaxis robertmarki vs. Diplotaxis brachyptera Vaurie , D. robertmarki being a distinctive species sympatric with P. benwarneri , and its putative “mother taxon,” D. brachyptera , having a somewhat similar (though generally in higher altitude locations) and wider discontinuous distribution to that of P. senex (sensu lato), with isolated populations of both the latter species demonstrating mild to moderate character shifts across their ranges.

The Phyllophaga “senex complex.” The Phyllophaga senex complex species share similar male genital structure, tarsal claws with only weakly serrate ventral edge, male 6 th abdominal ventrite with small prominent central lobe ( Fig. 7 , arrow) and female pygidial fovea. Phyllophaga senex (sensu lato) comprises several phenotypically distinct populations, most of which have males with functional flight wings and females that are flightless. The type locality of P. senex is the “Llano Estacado,” a large flat mesa running along much of the Texas-New Mexico border. “Typical” specimens of P. senex in and around the Llano Estacado tend to be somewhat lighter in color and are often smaller (e.g. Fig. 18–19 , a specimen from the Monahans dune system near Kermit, Texas) than more western and northern populations. Some southern Texas and New Mexico populations are uniformly even smaller and paler. Additional collecting is needed to further elucidate taxonomic limits and taxonomic status of

the other populations within this complex.

Applicable couplets from the Saylor’s (1940, p. 68) key to US Listrochelus males are here modified below to include males of P. benwarneri :

40(39). Pygidium very convex, densely and coarsely punctate and shining, with short procumbent hair; sixth

abdominal ventrite plane (genitalia fig. 6, k–n)................... Phyllophaga scuticeps (Bates) — Pygidium plane, very sparsely and finely punctate, with minute hair, surface subopaque; sixth abdominal

ventrite with a short and truncate lobe at middle (fig. 2, b [also Fig. 7 herein])................ 41

41(40). Flight wings functional (longer than elytra and folded beneath them); pronotum with anterior and posterior marginal beading weak; scutellum subtriangular; mesotibia with few setae mostly 1⁄5 or less as long as mesotibia............................................... Phyllophaga senex (Horn)

— Flight wings reduced, non-functional; pronotum with anterior and posterior marginal beading distinct, delimited by row of round punctures within; scutellum subsemicircular; mesotibia with moderately dense brush of setae mostly 1/4 to 1/3 as long as mesotibia... Phyllophaga benwarneri Warner , n. sp.

Remarks. Saylor (1940) misidentified females of a different species as the female of P. senex , because his description mentions a prominent transverse ridge on the occiput, a character that is not present in specimens of P. senex . Also, although describing the female tarsal claws as having a triangular tooth at middle in the species account (p. 115), Saylor separates P. senex out at the beginning of his key to females (1940, p. 68) as having tarsal claws “…lacking any intercalated larger teeth.” All female specimens of the “senex complex” examined are unique amongst USA Listrochelus in being flightless, with metathoracic wings shorter than the elytra. Additionally they lack a transverse ridge on the occiput, have a flat pygidium with medioapical fovea, and have all tarsal claws ventrally adorned with a slightly submedian triangular tooth and very weak serrations proximal to the tooth (e.g. Fig. 15–17 ); the serrations are usually obsolete distal to the tooth. Females of P. benwarneri may be distinguished from those of other members of the complex by having the scutellum nearly semicircular rather than triangular, and in having the clypeus biarcuate.

Sanderson (1958) tentatively determined two females of a dark brown form from “Flagstaff, Arizona ” (probably a sandy locality at lower elevations nearby) as Phyllophaga epigaea Wickham ; I examined these specimens and they are essentially identical to females of P. senex populations near Albuquerque, New Mexico ( Fig. 9, 11 ). The unusual facies of P. senex complex females indeed give them an appearance more similar to that of females belonging to the subgenus Eugastra than to other Listrochelus , the similarities apparently the result of parallelisms for flightlessness. The weak tarsal claw serrations may be easily overlooked, and this coupled with the unusual gestalt probably led to Saylor’s (1940) and Sanderson’s (1958) misidentifications.

Evans and Smith (2020) follow Rivera-Gasparín and Morón’s (2017) elevation of Listrochelus to generic status while maintaining as Phyllophaga subgenera other taxa scattered paraphyletically and polyphyletically in several more basal nodes than Listrochelus . Because there has yet to be a more comprehensive phylogeny of the New-World Rhizotrogini that includes a high level of taxon sampling, including many structurally similar Old-World groups and genetic sequencing data, I agree with recent authors such as Guzmán-Vásquez and Martínez-Martínez (2020) and Hernández-Cruz et al. (2019) and believe that it is premature to elevate Phyllophaga subgenera “piece-meal” and paraphyletically without a comprehensive analysis. Thus I am here retaining Listrochelus as a subgenus of Phyllophaga .

Figures

Figures 1–2.Male dorsal habitus of Phyllophaga species. 1) P. benwarneri. 2) P. senex, Albuquerque, New Mexico.

Figures 3–4. Male genitalia of Phyllophaga species, lateral view. 3) P. senex, Albuquerque, New Mexico. 4) P. benwarneri.

Figures 5–7. Males of Phyllophaga species. 5) P. benwarneri forebody, dorsoanterior view. 6–7) P. senex (Albuquerque, New Mexico): 6) Forebody, dorsoanterior view. 7) Pygidium (arrow points to 6th abdominal ventrite medial process).

Figures 8–11. Female Phyllophaga species dorsal and posterior habitus. 8, 10) P. benwarneri. 9, 11) P.senex, Albuquerque, New Mexico.

Figures 12–17. Phyllophaga benwarneri tarsal claws, lateral view. 12, 13, 14) Male pro-, meso- and metatarsi, respectively. 15, 16, 17) Female pro-, meso- and metatarsi, respectively.

Figures 18–19. Male Phyllophaga senex, Monahans Sand Dunes near Kermit, Texas. 18) Dorsal habitus. 19) genitalia, lateral view.