Polyphylla koso La Rue, 2016

La Rue, Delbert A., 2016, Natural history, ecology, and conservation of the genus Polyphylla Harris, 1841. 1. New species from the southwestern United States and Baja California, Mexico, with notes on distribution and synonymy (Coleoptera: Scarabaeidae: Melolonthinae), Insecta Mundi 2016 (491), pp. 1-41 : 7-10

Polyphylla koso La Rue , new species

( Fig. 6–10 , 52–53 )

Type material. Holotype. Male ( CASC #18339 ). Labeled “USA, CALIFORNIA, Inyo County, China Lake NAWS [Naval Air Weapons Station], Coso Mountains, Coso Bridge, 25.VII.1998, G. Pratt, C. Pierce, MV light” [phallobase and parameres mounted on card] . Paratypes. (8). Same data as holotype except 18.VII.1998, G. Pratt, M. van Tilborg (6 males) ; 19.VII.1999 (1 male); Mill Spring, 07.VI.2003, G. Pratt, C. Pierce, MV light (1 male). CASC, UCRC .

Description. Holotype. Male ( Fig. 6–9 ). Length 28.0 mm. Greatest width 12.0 mm. Humeral width 11.5 mm. Form. Elongate, robust, parallel-sided. Color. Head, eyes, pronotum, elytral calli, pygidium, and abdominal sternites black; elytra, scutellum, anterior clypeal margin deep rufotestaceous; basal antennomeres, other appendages of head, and legs rufotestaceous; lamellate antennomeres light testaceous; except where noted, setal and squamal vestiture white. Head. Subconvex; clypeus transverse with highly reflexed, feebly emarginate anterior margin; anterior angles obtuse; lateral margins basally reflexed and sinuate; disc deeply concave, coarsely punctate, with acuminate scales and recumbent setae. Frontoclypeal suture obscured medially by rugose punctation and contiguous acuminate scales and suberect setae. Frons depressed on either side of a longitudinal tumidity, surface moderately to coarsely punctate, provided with solitary to contiguous, acuminate scales and scattered setae. Vertex coarsely punctate, with similar vestiture as frons. Maxillary palpomere-4 elongate, cylindrical, anteriorly depressed, densely setose with minute, golden spiculae; 1/2 length of three basal palpomeres combined. Mentum subquadrate, anteriorly deeply emarginate, angles broadly rounded, disc posterolaterally with long setae. Antennae. Scape subtriangular, constricted basally, apex bulbous, provided with a dense scopula of long setae; lamellate antennomeres 4–10 distally recurved outward attaining a right-angle, provided with translucent, golden setae. Antennal club 2.5× (linear measurement) or 3.3× (curvilinear measurement) longer than basal antennomeres combined. Pronotum. Broadly convex, transverse, 2× wider than length at midline, widest at posterior 1/2; anterior angles sharply rounded, basal angles broadly obtuse and explanate; marginal bead absent anteriorly, serrate and explanate laterally, evanescent posteriorly. Disc moderately to coarsely punctate, punctures provided with an acuminate scale or suberect seta; medially sulcate, dividing a transverse tumidity at posterior 1/2; trivittate; vittae longitudinally complete, edges eroded, composed of contiguous to imbricate, acuminate scales. Scutellum. Oblong, broadly rounded; margins glabrous, disc obscured by imbricate scales; devoid of setae. Elytra. 2.2× greater in length than width; humeral angles obtusely rounded, posterolateral angles broadly arcuate. Marginal bead explanate and reflexed posterolaterally, evanescent posteriorly, sutural bead obscured by dense acuminate scales. Disc rugosely punctate; calli tumose, glabrous, moderately punctate; vestiture composed of solitary to imbricate, acuminate scales; devoid of setae; distinctly vittate; vittal edges coarsely eroded, composed of contiguous to imbricate, acuminate scales; sutural and subsutural vittae discontinuous; submarginal vittae complete; subhumeral vittae absent; interstitial area between discal and submarginal vittae with a series of disconnected, glomerate patches of squamae. Metathoracic wings functional. Pygidium. Subtriangular, convex; length subequal to width; angles obtusely rounded; disc moderately punctate, depressed behind reflexed margins; vestiture composed of contiguous, acuminate scales; devoid of setae. Venter. Densely pubescent obscuring pterothorax; exposed abdominal sternites subconvex with a basal glabrous band, vestiture composed of solitary to imbricate scales and solitary setae. Legs. Protibia bidentate, lacking any indication of a basal third tooth; dentition moderately separated, projecting obliquely forward from longitudinal tibial axis; inner margin rounded, outer margin with a sharp longitudinal carina; surfaces moderately to coarsely punctate with solitary, acuminate scales and setae. Meso- and metatibia lacking any indication of a transverse carina, dorsally coarsely to finely punctate, margins diverging toward apex at distal 1/3, provided with a fringe of thick spiculae. All femora flattened, margins converging toward apex, surface vestiture as protibiae. Apices of tarsomeres coronate with a fringe of short, translucent spiculae; tarsomere-5 elongate, subequal in length to four basal tarsomeres combined, ventral surface bearing a fine carina extending length of tarsomere; tarsal claws with basal proximal tooth. Phallobase and parameres. Number examined (3). In dorsal aspect, symmetrical with two simple parameres narrowing distally, apices diverging outward; median notch sharply rounded, separated less than 1/2 length of parameres; lateral aspect, apical 1/4 cristate with apices smoothly rounded ventrally; caudal aspect, obliquely depressed; distal tips separated, gradually diverging outward at apex.

Female. Unknown.

Variation. Males (8). Length 26.0–28.0 mm. Greatest width 11.5–12.5 mm. As holotype except: Color. Pronotal discal surface rufotestaceous; tarsal claws and protibial dentition black; femora deep rufotestaceous. Head. Setal and squamal vestiture pale yellow, variably reduced or obscuring disc; antennal lamellae broadly obtuse. Pronotum. Squamal vestiture pale yellow; setal vestiture reduced; posterolateral bead coarsely serrate. Elytra. Discal vittae incomplete, coarsely eroded, reduced to clumps of imbricate squamae ( Fig. 10 ); subhumeral vittae present. Pygidium. Surface obscured by dense, squamal vestiture. Legs. Apices of protibial dentition worn; setal and squamal vestiture reduced (abrasion?).

Diagnosis. The coarsely eroded elytral vittae, deep rufotestaceous integument, and eastern California distribution of P. koso are similar to its adelphotaxon, P. aeolus . However, males of P. aeolus have pale yellow setae; a combination of pale yellow or white squamae (setal and squamal vestiture white in P. koso ); interstitial squamae contiguous with elytral vittae (intermittent in P. koso ); elytral sutural vittae continuous and complete (fragmented and eroded in P. koso ); elytral discal setae (absent in P. koso ); and distinctly larger antennal structure than in P. koso . Ecologically, P. aeolus is a psammophilous obligate endemic to the Kelso Sand Dunes, San Bernardino County, California, whereas, P. koso is a montane isolate associated with relictual pinyon-juniper woodlands.

In some respects, P. koso is similar in appearance to some phenotypes of P. arguta which lacks pronotal setae; has a light testaceous to black elytral integument; and is primarily restricted to the Great Basin in Nevada and Utah.

Natural history. Males of P. koso were collected at mercury vapor lights in pinyon-juniper woodlands between 2100–2300 m during July with one record during early June. Other specimens have been collected during early August ( Ballmer 2003). Polyphylla koso is sympatric with the southwestern montane form of P. decemlineata .

An unidentified species of Pyrgota Wiedemann ( Diptera : Pyrgotidae ), a dipteran genus of endoparasitoids of Melolonthinae, has been observed to parasitize P. koso while avoiding the more abundant P. decemlineata (G.F. Pratt, in litt.). Typically, the female pyrgotid oviposits on the exposed abdomen of the beetle while in flight possibly utilizing one or a combination of olfactional mechanisms, microhabitat association, or synchrony with the host life cycle to localize and distinguish its preferred host. Pratt (1943), Young (1967, 1988), Salehi (1984), and Skelley (2009) described similar dipteran parasitism on other Polyphylla species.

Ecology. The Coso Mountain Range is located in the Mojave Desert in east central California with elevations from 610 to 2490 m at Coso Peak. These remote mountains are part of the Great Basin “sky island archipelago,” a complex of high desert ranges that were geographically and ecologically isolated during the Pleistocene ( Heald 1951; Smith and Street-Perrot 1983; Warshall 1995; Baldwin and Martens 2002). Because of an array of soils, microclimates, and topographic complexities, these isolated mountain ranges provide habitats for many rare and endemic species and are among the most biodiverse ecosystems in North America. Consequently, their associated faunas are highly divergent from other closely related taxa ( Marshall 1957; MacArthur and Wilson 1963, 1967; Warshall 1995; Coblentz 2005).

At the type locality, Coso Bridge ( Fig. 52 ), southwest of Coso Peak at approximately 2286 m elevation, Pinus monophylla Torrey and Frémont (single-leaf pinyon: Pinaceae ) is predominant with a mixed understory of Artemesia tridentata ssp. Nuttall (big sagebrush: Compositae), Eriogonum nudum Bentham (naked buckwheat: Polygonaceae ), E. umbellatum Torrey (sulphur-flower buckwheat: Polygonaceae ), E. wrightii Torrey ex Bentham (wright’s buckwheat: Polygonaceae ), Purshia glandulosa Curran (desert bitterbrush: Rosaceae ), and Ribes velutinum E. Greene (desert gooseberry: Grossulariaceae ) (G.F. Pratt, in litt.).

At Mill Springs ( Fig. 53 ), approximately 2130 m elevation where a single specimen was collected in early June, vegetation is primarily Juniperus occidentalis Hooker (western juniper: Cupressaceae ) (G.F. Pratt, in litt.).

Because the mountains lie within the rain shadow of the Sierra Nevada Range, annual precipitation averages between 12.5 and 30.5 cm. Much of this occurs as snow at higher elevations which is often present until late spring. Average annual temperatures range from 4.0° to 19° C., with 125 to 250 frost-free days. Soils are well drained with rapid surface runoff from alluvial fans that lead to either the adjacent Owens or Panamint Valleys.

Despite the generally dry conditions, the areas surrounding Coso and Mill Springs support areas of unique flora including species that exemplify vastly disjunct distributional ranges (G.F. Pratt, in litt.). In arid regions where moisture availability constrains species distributions, a locally damp site will act as an ecological refugium.

The Coso pinyon-juniper woodland represents a relictual population of a more widespread coniferous forest that dominated much of southwestern North America during the Pleistocene. Polyphylla koso may have been more widely distributed at that time when this region of eastern California was a broad savanna dominated by shallow pluvial lakes with scattered woodlands occurring at all elevations ( Axelrod and Ting 1960; Woodcock 1986; Mensing 2001). As climate transitioned to interstadial conditions between 14,000 and 10,000 years ago, large contiguous areas of cooler temperate habitats were fragmented into mountain-top refugia and replaced at lower elevations by a cactus-legume-dominated desert scrub ( Wells and Woodcock 1985; Thompson et al. 1993; Thompson and Anderson 2000).

Conservation. The distribution of P. koso lies within the boundaries and jurisdiction of the China Lake Naval Air Weapons Station. As a result, public access to the area is extremely limited which affords it some protection. However, because it occupies a very limited geographic range, P. koso should be considered a species of “special concern.”

Remarks. Polyphylla koso is the second species of Nearctic Polyphylla restricted to a small area of an isolated mountain complex. The other species is P. hirsuta Van Dyke (1933) of the Patagonia Mountains, Santa Cruz County, Arizona.

Although the type locality of P. barbata is “Mt. Hermon, Santa Cruz County, California ” ( Cazier 1938), the name “Mount Hermon” was chosen for a Christian retreat site for its biblical significance rather than montane characteristics (elevation 178 m).

Etymology. From the Tümpisa Shoshone language, kosoowah meaning “to be steamy,” referring to the numerous hot springs throughout the area and its indigenous paleo-inhabitants, the Koso. The name is applied as a noun in apposition.

Common name. The Koso Mountains polyphyllan scarab beetle.

Figures

Figures 6–10. Polyphylla koso. 6–9) Holotype male. 10) Left elytron of paratype male.

Figures 50–57. Habitats. 50–51) Polyphylla anivallis. Animas Valley Sand Dunes, Hidalgo Co., NM. 52–53) Polyphylla koso. Coso Mountains, Inyo Co., CA. 52) Coso Bridge. 53) Mill Springs Canyon. 54–55) Polyphylla morroensis. Baywood Fine Sands, San Luis Obispo Co., CA. 56–57) Polyphylla socorriana. El Socorro Sand Dunes, Baja California, MX.