Dichelonyx magnesae 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 magnesae

description: Dichelonyx magnesae McPeak and Lago, new species
Zoobank.org/ urn:lsid:zoobank.org:act: DE31A932-046B-4DAD-BC07-3B71F9250954 (Figs. 1–10)
Type Material. 66♂, 128♀. Holotype labeled: a) “ USA:CA: San Diego Co., / Aguanga Mtn. / 4.2 mi W Hwy 79 on / 9S07 Rd, 4200’, BL & MV”; b) “ 33°19.587’N, 116°44.925’W / 14-15 June 2012, leg. R. H. / McPeak & R. A. Cunningham ”; c) on red paper, “ HOLOTYPE / Dichelonyx magnesae / McPeak & Lago” (1♂ CASC) (Fig. 1). Allotype female labeled as holotype except for c) on red paper “ ALLOTYPE / Dichelonyx magnesae / McPeak & Lago” (1♀ CASC). Paratypes, each with our yellow paratype label: 43♂ and 92♀ with same label data as holotype (2♂, 2♀ CASC; 2♂, 2♀ CSCA; 2♂, 2♀ AVEC; 2♂, 2♀ EMEC; 2♂, 2♀ FSCA; 2♂, 2♀ LACM; 2♂, 2♀ OJSM; 2♂, 2♀ PKLC; 8♂, 25♀ RACC; 7♂, 39♀ RHMC; 2♂, 2♀ SBMNH; 2♂, 2♀ SDNHM; 2♂, 2♀ TAMU; 2♂, 2♀ UCDC; 2♂, 2♀ WBWC; 2♂, 2♀ WFBM); 15♂ with label data same as holotype, except a) “blacklight”; b) “ 5 July 1992, R. H. McPeak ” (2♂ CASC; 8♂ RHMC; 5♂ SDNHM); 2♂ labeled “ Lake Henshaw / San Diego Co., CA / V-25-92, At light / W. F. Chamberlain” (2♂ TAMU); 1♀ labeled “CA: San Diego Co., / Warners, / VI/25/1925 ” (1♀ CASC); 1♀ labeled “CA: San Diego Co. / 1.5 mi W. of Warner / Springs on Hwy 79 / 2900’ VII-5-92 / R. H. McPeak ” (1♀ RHMC); 1♀ labeled “CALIF: San Dgo. Co. / 7 mi. NNW Warners / Sprs, Indian Flats / Campgd., VIII- 20-76 / P. Rude collector”; b) “ Adenostoma ” (1♀ EMEC); 1♂, 2♀ labeled “ Pine Valley / San Diego Co, Calif / VI/28/86 / R. H. McPeak ” (1♂, 2♀ RHMC); 1♂ labeled “ USA:CA: San Diego Co. / Buckman Springs. Rd., / 1.5 km S Cottonwood / Crk.; 32.706°, -116.490° / June 17, 2017; at UV / light; W. B. Warner ” (1♂ WBWC); 22♀ labeled “ Bautista Canyon / 7 mi. SE Hemet / Riv. Co. Calif. / 23-June-1970 ”; b) “Black lite / J. Saulnier ” (5♀ RACC, 17♀ RHMC); 2♀ labeled “ Bautista Canyon / 7 mi. SE Hemet / Riv. Co., Calif. / 23-June-1985 ”; b) “ R. A. Cunningham coll.” (2♀ RACC); 4♀ labeled “ Bautista Canyon / 13 mi. S. San Jacinto / Riverside Co., Calif. / VI/27/1972 / S. Bennett ” (4♀ RHMC); 2♂ labeled “ Coahilla Mtn. Trail / San Bern. Nat. Forest / Riverside Co. Calif. / VII/3/1972 / S. Bennett ” (2♂ RHMC); 1♀ labeled “ MEXICO: Baja Calif / 12 mi E Catavi ~ na / 4 VI 1997 / light sheets”; b) “ William D. Shepard leg.” (1♀ RHMC); 1♀ labeled “ MEXICO: Baja Calif. / Mike’ s Sky Rancho / 3 VI 1997 / light sheets”; b) “ William D. Shepard leg.” (1♀ RHMC); 1♂ labeled “ MEX., BajaCalif. N, Sierra / Juarez 5 mi. N La / Huerta, VI-9-70 / E. L. Sleeper collr.”; b) “California State / Univ. Long Beach / 1996 donation to / Calif. Acad. Sci.” (1♂ CASC).
Description. Holotype male. Length 7.4 mm. Head and pronotum medium brown; elytra paler, yellowish brown or testaceous with light green luster (Fig.2). Dorsum and venter setose, setae golden-yellow dorsally, light yellow ventrally, with density varying from sparse to dense, glabrous patches present on vertex, pronotum, elytra, and mesosternum. Head: Clypeus strongly reflexed, anterior angles broadly rounded, anterior margin truncate, lateral margins divergent to base; surface densely and coarsely punctate; frontoclypeal suture sinuate, with the center extending farther posteriorly than the lateral arms. Clypeus and head uniformly covered with dense, posteriorly directed, prostrate setae, except for a broad, glabrous, impunctate triangle on vertex (Figs. 3–4). Antenna testaceous or slightly infuscate, with 9 antennomeres, club approximately same length as funicle. Maxillary palpus testaceous or slightly infuscate, terminal segment nearly cylindrical, base and apex abruptly narrowed. Pronotum: Lateral margins obtusely angulate at apical 1/3, edges straight, shallowly crenulate before and after angulation; anterior angles nearly 90°, posterior angles obtuse but apparent; midline vaguely depressed (sulcus), more heavily punctate than adjacent smooth areas; disc in lateral half and along apical and basal margins densely punctate and setose, setae obscuring surface. Disc with 2 more or less rectangular, mostly glabrous, finely and sparsely punctate maculae on either side of midline. Scutellum densely setose. Elytra: Color primarily testaceous, with light metallic green reflections; suture, base, and portions of lateral margins infuscate, infuscation narrowly outlining scutellum, extending across anterior face of humeral umbone and lateral margin under and slightly behind umbone; setae recumbent, much sparser than pronotum, most numerous mesad of a line drawn from humeral to apical umbones, without bare costae (not vittate); laterally, setae shorter, semi-erect, and less obvious (Fig. 5). Discal costae vaguely indicated. Venter: Meso- and metathoraces and abdominal sternites covered with light yellow (appearing light gray because of dark integument beneath), plumose, scale-like setae. Metacoxae, metepisternum, mesepisternum, anterior region of proepimera, pygidium, and posterior 2/3 of propygidium very densely setose. Metasternum densely setose on lateral thirds, but central disc nearly glabrous except for a few suberect, simple setae. Proepimeron setose anteriorly, with transverse glabrous area posteriorly. Legs: Testaceous. Metatibial spurs unequal in length, with short spur 0.7× length of long spur; both spurs rather narrow with base slightly enlarged, longer spur parallel-sided, gently curved, narrowly rounded apically; shorter spur narrowed from base to apex. Genitalia: Parameres typical for genus; in lateral view, dorsum slightly angulate, apical lobes relatively robust, with down-curved, acute apices (Fig. 6). Internal sac without sclerites.
Allotype Female. Length 8.4 mm. Anterior clypeal angles broadly rounded and lateral margins divergent at base (Figs. 7–9). Antennal club about half length of funicle. Coloration similar to male, except glabrous areas of pronotum larger with better defined borders, narrowly infuscate margins of elytra slightly more extensive across anterior margin and under humeral umbone, lateral marginal bead of elytra infuscate along entire length (Fig. 10). Elytral pubescence similarly distributed, but obviously shorter, area between discal patch and outer setose interval with short “microsetae,” barely longer than diameter of punctures from which they emerge. Abdomen robust, convex ventrally in profile, rather than flattened or concave as is characteristic of males. Other external characters similar to male.
Variation. Dichelonyx magnesae males range from 6.9 to 8.3 mm in length, while females range from 7.7 to 8.9 mm. In typical (most common) specimens and darkest specimens, the two large, impunctate, glabrous rectangles on either side of the depressed pronotal midline (sulcus) are dark reddish brown or piceous, with the densely punctate medial depression, anterior, posterior, and lateral areas setose and light reddish brown (color differences may be difficult to see on densely setose individuals). In pale specimens, the pronotum may be uniformly light reddish brown. The maculae vary from completely bare to uniformly covered with sparse setae, but the areas are always distinct from the densely punctate, generally densely setose marginal areas. The shape of the maculae is variable,rectangular to rounded, sometimes coalescing anteriorly to form an inverted, cordate, unified macula.
The darkened margins on the elytra usually extend from the lateral margin across the anterior face of the elytra, including irregular incursions on the base of the disc, along the lateral margins of the scutellum, and the complete length of the sutural intervals, but never including the dorsal surface of the humeral umbone. The darkest specimens may have the base more extensively, but unevenly, darkened, surpassing the tip of the scutellum medially by about the length of the scutellum, but not extending broadly along the suture. In addition, the lateral margins of the elytra may be darkened, including the anterior and lateral faces of the humeral umbone, anterior surfaces of the ninth costae, ninth interval, and marginal bead back to the level of the first or second sternite, and the lateral marginal bead may be darkened to the apex. The base color of the disc may be light reddish brown, but this is uncommon. In the palest specimens, most basal infuscations may be absent, with only the margins along the scutellum and extreme inner margins of the sutural intervals clearly darkened. Elytral setae are densely spaced over the entire surface in males and on the central disc in females (often missing apically, basally, and occasionally medially in females), generally not interrupted by glabrous costae. Rarely, males have the third costa vaguely visible through the setal coat.
Natural History. A single specimen was taken on A. fasciculatum (chamise). All other specimens from San Diego County (161) were taken at blacklight or mercury vapor light in chaparral habitat. The most southerly specimen examined was labeled 12 mi. E of Catavi~ na, Baja California, Mexico (Fig. 1). The habitat east of Catavi~ na is Central Desert, dominated by several species of cacti, elephant trees, and boojum trees. We suspect that this specimen was mislabeled and is from another locality.
Etymology. Dichelonyx magnesae is named in honor of Mary Agnes McPeak, wife of the first author. Mary was frequently called “Magnes” and the person who urged the first author to take a course in entomology taught by Dr. E. L. Sleeper. Her entomological urging resulted in a life-long interest in scarab beetles by the first author.
Diagnosis. Males of D. magnesae are distinguished from D. bajaensis males by their rounded to broadly rounded anterior clypeal angles (Figs. 3–4); yellow or gold setae that are evenly distributed over the entire elytral surface or, occasionally, less dense on lateral third (Figs. 2, 5); third and fifth costae rarely glabrous, forming thin lines in discal setal patches; and parameres in lateral view with dorsum slightly angulate, apical lobes relatively robust, with down-curved, acute apices (Fig. 6). Males of D. bajaensis have anterior clypeal angles nearly 90 ⁰ (Figs. 11–13); elytra clearly vittate (Fig. 14) or not (Fig. 15); and parameres in lateral view slightly angulate dorsally, but angulation less evident than in D. magnesae, with down-curved, acute apices sharper than in D. magnesae (Fig. 16). Males of D. pusillus are distinguished from D. magnesae and D. bajaensis males by their typically uniform dark brown coloration and white or silvery white elytral setae that are generally distributed in distinct vittae, but occasionally not (Fig. 20).
Females of D. magnesae are distinguished from those of D. bajaensis by the broadly rounded clypeal angles (Figs. 8–9) and typically testaceous elytra with the suture completely darkened but never expanded into a broad triangular area surrounding the scutellum (Fig. 7). Females of D. bajaensis have elytral coloration typically testaceous, with the suture completely darkened and expanded into a broad triangular or, rarely, rectangular area around the scutellum (Fig. 11). The clypeal angles of D. bajaensis are not broadly rounded as in D. magnesae (Figs. 18–19). Females of D. pusillus are distinguished from those of D. magnesae and D. bajaensis by the dark coloration and white or silvery white elytral setae (Fig. 25).
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 46-51, DOI: 10.1649/0010-065X-74.1.45, http://zenodo.org/record/4790442