Dichelonyx
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

description: KEY TO THE SPECIES OF DICHELONYX WITH LONGITUDINAL PRONOTAL SULCI AND FROM SOUTHERN CALIFORNIA, USA AND BAJA CALIFORNIA, MEXICO
1. Elytra bright metallic green or blue; length 8.5–13.7 mm (Fig. 27) ............................ ........................ Dichelonyx vicinus (Fall)
1 ʹ. Elytra testaceous (Fig. 2) to dark brown (Fig. 14), either lacking metallic sheen or with light yellowish green reflections; length generally less than 8.5 mm (specimens of D. pusillus may reach 9.0 mm, but these are never bright metallic green) ..................................... 2
2. Males; abdomen flattened in lateral view, apical 2 segments slightly concave ventrally; antennal club relatively long, subequal to length of funicle (Fig. 2) ....................... 3
2 ʹ. Females; abdomen convex ventrally; antennal club shorter, about half length of funicle (Fig. 7) .............................................. 5
3. Anterior clypeal margin truncate to slightly concave (most easily seen at an angle from above and behind the head), anterior angles nearly 90° (Figs. 12–13), narrowly rounded; lateral margins straight and parallel. Elytra not clearly vittate or vittate (Figs. 14–15). Typically, impunctate areas on pronotal disc dark brown, punctate areas testaceous, elytral disc testaceous, with suture, large triangular area surrounding scutellum, and anterior margin in front of humeral umbone infuscate, darkened areas showing metallic green reflections (some specimens fairly uniform brown with infuscate margins, but clypeal shape remains distinctive) (Fig. 11)……………… Dichelonyx bajaensis McPeak and Lago, new species
3 ʹ. Anterior clypeal margin truncate to convex (most easily seen at an angle from above and behind the head), anterior angles slightly rounded to broadly rounded (Figs. 3–4, 21–22); lateral margins slightly to strongly converging anteriorly. Elytra vittate or not, dorsal coloration testaceous to dark brown ... ......................................................... 4
4. Elytra vittate, with longitudinal stripes of white or silvery, recumbent or semierect, coarse setae; costae glabrous or nearly so, often wide, nearly half to 2/3 as wide as setal stripe (Fig. 20). Dorsal coloration brown, typically unicolored, but occasionally central elytral disc lighter, rarely only elytral margins infuscate, generally without light yellowish green metallic reflections ......................... ................. Dichelonyx pusillus (LeConte)
4 ʹ. Elytra without distinct vittae, discal setae fine and dense, yellow or gold, evenly distributed over entire surface, or less dense on lateral third (Figs. 2, 5); rarely 3 rd and 5 th costae glabrous, forming thin lines in discal setal patches, but these lines not more than 20% as wide as patches of setae and usually not visible beyond 2/3 elytral length. Dorsal coloration usually bicolored; glabrous patches on pronotum light to dark brown (Fig. 2), punctate areas usually lighter; elytra testaceous (rarely light brown), with suture, anterior margin, and lateral area under humeral umbone darkened (Fig. 2) (occasionally, lateral margin darkened to level of apical umbone; in palest individuals, only suture infuscate); all darkened areas may be expanded slightly in darkest specimens, darkened areas and entire elytral disc with light metallic reflections ……………………… Dichelonyx magnesae McPeak and Lago, new species
5. Elytra unicolorous, medium to dark brown, or with margins slightly darker than disc; pronotum unicolorous dark brown. Elytra vittate, with longitudinal stripes of white or silvery, recumbent or semierect, rather sparse, coarse setae; costae glabrous or nearly so, often wide, nearly half as wide as setal stripe…………… …………… Dichelonyx pusillus (LeConte)
5 ʹ. Elytra usually testaceous with suture and anterior margins very dark; pronotum with impunctate areas on either side of midline medium to dark brown, with midline and punctate lateral areas paler (surface often obscured by thick setal coat). Elytra usually not vittate, discal setae mostly recumbent, dense, often restricted to disc mesad of a line from humeral umbone to apical umbone; occasionally, 3 rd and 5 th costae glabrous, thus stripes of setae become apparent, but glabrous lines very thin, not exceeding 20% of setal patch width; discal setae may be absent or nearly so ............................................ 6
6. Elytra typically testaceous, with suture completely darkened and expanded into a long, broad triangular area surrounding scutellum extending from near midpoint of elytra to inside humeral umbones (rarely, “triangle” is more like a rectangle), darkened area continuing across anterior face of elytra to lateral margin, which may be light or broadly darkened to the level of the apical umbone (dark, rather uniformly brown specimens are not uncommon); elytral disc generally covered with setae mesad of a line extending from humeral to apical umbones; clypeal margin nearly truncate when viewed from angle from above and behind, depth of recurved face uniform from side to side; setae on dorsal surfaces whitish …………………… ………………………… Dichelonyx bajaensis McPeak and Lago, new species
6 ʹ. Elytra typically testaceous with suture completely darkened, but never expanded into a long, broad, triangular area around scutellum, instead, base of elytra broadly darkened along scutellum and across anterior face of elytra to lateral margin, which may be pale or broadly darkened for 2/3 elytral length; occasional specimens uniformly light brown, but at least elytral sutural margin infuscate; elytral disc often nearly glabrous or inconspicuously setose; clypeal margin broadly rounded (viewed from angle from above and behind), recurved face deepest medially, shorter at sides; setae on dorsal surfaces, particularly on pronotum, yellow or golden …… Dichelonyx magnesae McPeak and Lago, new species
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 57-58, DOI: 10.1649/0010-065X-74.1.45, http://zenodo.org/record/4790442