Dichelonyx bajaensis McPeak and Lago 2020, new species
Creators: name: McPeak, Ron H.
name: Lago, Paul K.
name: Hanley, Guy A.
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Melolonthidae
Dichelonyx
Dichelonyx bajaensis

description: Dichelonyx bajaensis McPeak and Lago, new species
Zoobank.org/ urn:lsid:zoobank.org:act: 5CC98646-67AD-4DF4-9398-1D27E28F798F (Figs. 1, 11–19)
Type Material. 21♂, 13♀. Holotype labeled: a) “B. CALIF. N., / Sa. Juarez 13.5 mi. / S El Rayo”; b) “ E. L. Sleeper / Collr. VI-8-70”; c) “California State / Univ. Long Beach / 1996 donation to / Calif. Acad. Sci.” (1♂ CASC) (Fig. 1). Allotype female labeled as holotype (1♀ CASC). Paratypes, each with our yellow paratype label: 3♂, 5♀ with same label data as holotype (3♂, 5♀ CASC); 2♂, 2♀ labeled “B. CALIF. N. / 2.2 mi. S / El Topo VI-6-70”; b) “ E. L. Sleeper / Collr.”; c) “California State / Univ. Long Beach / 1996 donation to / Calif. Acad. Sci.” (2♂, 2♀ CASC); 2♂, 2♀ labeled “B. CALIF. N., / Sa. Juarez 3.6 mi / SE El Rayo”; b) “ E. L. Sleeper / VII-2-60 Collr.”; c) “California State / Univ. Long Beach / 1996 donation to / Calif. Acad. Sci.” (2♂, 2♀ CASC); 8♂, 1♀ labeled “ MEXICO: BajaCal. Norte / Sierra Juarez, 3 mi. / S. of Mexicali-Tecate / Hwy. along road to”; b) “El Topo Ranch 20-VI- / 1973 S. C. Williams & / K. B. Blair CSW # 313” (8♂, 1♀ CASC); 1♂, 1♀ labeled “ MEX., BajaCalif. N, Sierra / Juarez 5.7 mi. N Rosa / del Castilla, VI-10-70 / E. L. Sleeper Collr. ”; b) “California State / Univ. Long Beach / 1996 donation to / Calif. Acad. Sci.” (1♂, 1♀ CASC); 1♂ labeled “B. CALIF. N. / 10 mi. E San / Jose Castillo”; b) “Blacklight”; c) “ E. L. Sleeper / Collr.” d) “California State / Univ.Long Beach / 1996 donation to / Calif. Acad. Sci.” (1♂ CASC); 3♂, 1♀ labeled: “CA: San Diego / Boulevard / at light, VI-9- 94 / R. H. McPeak. ” (2♂, 1♀ RHMC; 1♂ PKLC).
Description. Holotype male. Length 6.2 mm. Clypeus light brown, frons and vertex dark reddish brown; pronotum similarly bicolored, glabrous rectangles on either side of midline dark reddish brown, midline and all marginal areas light brown; elytra primarily yellowish brown or testaceous, with suture, broad, triangular area surrounding scutellum, base across anterior face of humeral umbone, and lateral marginal bead infuscate (Fig. 11). Dorsum and venter covered with sparse to dense, recumbent setae; vertex, pronotal disc laterad of midline, and central metasternum glabrous and shiny. Head: Clypeus strongly reflexed, anterior angles narrowly rounded; en face, anterior margin truncate (Figs. 12–13): viewed from above and behind, anterior angles prominent with anterior margin concave between them, lateral margins nearly straight, parallel to base; surface densely and coarsely punctate; fronto-clypeal suture sinuate, arcuate posteriorly in middle. Clypeus and head covered with dense, posteriorly directed, prostrate, golden-yellow setae, except vertex glabrous and distinctly punctate laterally, impunctate medially. Antennae testaceous, with 9 antennomeres, club approximately same length as funicle. Maxillary palpi testaceous or light brown, terminal segment nearly cylindrical, base and apex narrowed. Pronotum: Lateral margins obtusely angulate just before mid-length, straight and coarsely but shallowly crenulate before and after angulation; anterior angles slightly obtuse, posterior angles broadly obtuse but evident; midline vaguely depressed; rectangular areas on either side of midline glabrous, slightly raised, with scattered fine punctures and few sparse setae. Apical and basal regions, depressed midline, and lateral thirds densely punctate and covered with light yellow or dirty white setae that obscure pronotal surface. Scutellum densely setose. Elytra: Color primarily testaceous, with suture, base, anterior face of humeral umbone, and lateral marginal bead dark brown to piceous, darkened areas exhibiting light metallic green reflections; recumbent setae dense in medial half of each elytron, sparse and scattered near base; 1 st discal costa apparent, slightly dividing setose field basally, becoming indistinct in apical half, other discal costae indistinct, except for distinct submarginal (9 th) costa; area between discal setose field and submarginal costa sparsely covered with short setae, appearing nearly glabrous in middle, space between submarginal costa and lateral margin with long, relative sparse setae; humeral umbone and irregular areas adjacent to scutellum glabrous, or nearly so (Figs. 11, 14–15). Venter: Meso- and metathoraces covered with white, recumbent setae. Metasternum densely setose on lateral thirds, with disc glabrous except for scattered suberect simple setae. Metacoxae, metepisternum, mesepisternum, lateral regions of proepimeron, pygidium, and posterior 2/3 of propygidium densely setose. Proepimeron setose anteriorly and posteriorly, but with transverse glabrous area beneath lateral angle. Legs: Testaceous. Metatibial spurs unequal in length with short spur 0.7× length of long spur; both spurs rather narrow, longer spur parallel-sided, narrowly rounded apically; shorter spur narrowed from base to apex. Genitalia: Parameres typical for genus, slightly angulate dorsally, angulation less evident than in D. magnesae, apically elongate lobes less robust in lateral view compared to those of D. magnesae, with down-curved, acute apices sharper than apices in D. magnesae (Fig. 16). Internal sac without sclerites.
Allotype Female. Length 6.7 mm. Antennal club about 0.7× length of funicle. Anterior clypeal angles rounded and lateral margins divergent at base (Figs. 17–19). Coloration similar to male, except glabrous areas of pronotum larger and bearing scattered setae basally and apically, infuscated triangle surrounding scutellum more extensive than in male (Fig. 17), humeral umbone with infuscate streak extending posteriorly about 1/3 elytral length, lateral marginal bead not infuscate. Elytral pubescence similarly distributed but shorter than in males, area between discal patch and outer setose interval apparently glabrous, but actually with short microsetae. Abdomen robust, convex ventrally in profile, rather than concave as is characteristic of males. Other external characters similar between the sexes.
Variation. Dichelonyx bajaensis males range from 6.0 to 7.8 mm in length, while females range from 5.7 to 8.0 mm. Typical specimens have bicolored pronotum and elytra. The glabrous rectangles on either side of the depressed pronotal midline are dark reddish brown or piceous, with the densely punctate medial depression, and anterior, posterior, and lateral areas setose and light reddish brown (color differences may be difficult to see on densely setose individuals). The “glabrous” rectangles vary from completely bare to uniformly covered with sparse setae, but the rectangles are always easily distinguished from the heavily punctate, densely setose midline and marginal areas. Unlike the condition seen in D. magnesae, uniformly brown individuals are common, and these show no difference in color between the different areas on the pronotum.
Like typical specimens of D. magnesae, the elytra of D. bajaensis are usually testaceous with darkened margins, the latter usually extending from the lateral margin across the anterior face of the humeral umbone, then invading the disc as a broad macula on either side of the scutellum and narrowing to the sutural interval just short of the midpoint of the elytra (rarely less than 3× length of scutellum). The margins of the macula are variable, sometimes projecting apically along the third costa, resulting in a somewhat rectangular appearance. The complete length of the sutural intervals is darkened, the lateral margins darkened to varying degrees, from a short line under the humeral umbone to broadly infuscate nearly to the apex. Brown individuals, both males and females, show considerable variation in coloration, but all lack the triangular elytral macula. Some are uniformly light brown on the pronotum and elytra, lacking elytral maculae and infuscate margins, or they may have the sutural intervals lightly infuscate. Others have the pronotum and lateral and sutural margins darker than the elytral disc. Eighteen of 34 specimens examined were brown and lacked elytral maculae. In general, elytral setae are white, densely spaced medially (often missing apically and basally), without evidence of exposed costae, and mostly absent on lateral thirds in both sexes. Occasional individuals have the third costa (first costa apparent after sutural costa) glabrous in the basal half or intermittently bare for entire length. Fewer specimens have the third and fifth costae bare, or nearly so, for their entire length.
Natural History. Specimens of D. bajaensis were collected in chaparral habitat in Baja California, Mexico and San Diego County, USA. The species composition of chaparral varies depending on slope, aspect, and elevation. Chamise and red shank (Adenostoma sparsifolium Torrey) are widely present, accompanied by a mixture of Ceanothus L. (Rhamnaceae), Arctostaphylos Adans. (Ericaceae), and Quercus L. (Fagaceae). Specific data for the specimens collected in Baja California are not known. The four specimens collected at Boulevard, San Diego County, were taken at light.
Etymology. The first specimens of D. bajaensis discovered in the California Academy of Science collection are from Baja California, Mexico. The specific epithet recognizes the area of collection.
Diagnosis. Dichelonyx bajaensis is distinguished from D. magnesae and D. pusillus in the diagnosis for D. magnesae.
description: Published as part of McPeak, Ron H., Lago, Paul K. & Hanley, Guy A., 2020, Two New Sulcate Species of Dichelonyx Harris (Coleoptera: Scarabaeidae: Melolonthinae: Dichelonychini) from Southern California, USA and Baja California, Mexico, pp. 45-59 in The Coleopterists Bulletin 74 (1) on pages 51-56, DOI: 10.1649/0010-065X-74.1.45, http://zenodo.org/record/4790442