Macrodactylus, Dejean, 1821

Arce-Pérez, Roberto & Morón, Miguel Ángel, 2020, Review of the species of Macrodactylus Dejean (Coleoptera: Scarabaeidae Melolonthinae) from the Central American Nucleus, Zootaxa 4772 (3), pp. 567-584 : 582-584

Key to species of Macrodactylus from the Central American Nucleus

(Adapted from Arce-Pérez & Morón 2005, 2011)

1. Basal half of tarsomeres ringed with setae or with few scattered white setae...................................... 2 – Basal half of tarsomeres without white setae.............................................................. 11

2(1) Tarsomeres with few, scattered white setae in basal half; body integument totally reddish yellow and completely covered with reddish yellow vestiture; vestiture less dense near elytral margins; tarsi and apices of tibiae black (Fig. 56). Genitalia: male (Figs. 81–82); female (Fig. 83). Mexico, Guatemala, and El Salvador.................. Macrodactylus zunilensis Bates

– Tarsomeres with obvious rings of white setae in basal half; integument of the body of variable colour, vestiture dorsal variously arranged.............................................................................................3

3 (2) Length less than 10 mm; male profemora with acute triangular basal projection, slightly twisted at the apex; integument of the body glossy black with greenish-yellow iridescence; elytra and legs reddish yellow; elytra covered by uniformly distributed pale yellow setae (Figs. 1, 3); parameres short, oval, glabrous (Figs. 5–7); female genitalia (Fig. 8). Guatemala......................................................................... Macrodactylus eniocanoi Arce-Pérez & Morón

– Length greater than 10.5 mm; male profemora with subrectangular basal projection, integument of the body of variable colour, vestiture dorsal absent or variously arranged; parameres circular or oval, with rows of setae on lateral margins (Figs. 21, 39). ................................................................................................... 4

4 (3) Elytra glabrous....................................................................................... 5 – Elytra setose......................................................................................... 7

5 (4) Elytra black with blue steel reflections (sometimes opaque in old specimens); antennal flagellum, legs, and pygidium reddish yellow (Fig. 14). Genitalia: male (Figs. 27–28); female (Fig. 29). Mexico and Guatemala....................................................................................................... Macrodactylus championi Bates

– Elytra at least partly reddish-orange; antennal flagellum, legs, and pygidium reddish orange.......................... 6

6 (5) Length approximately 10.5 mm, prosternal process strongly bifid with acute apex; protibiae with long and thick setae in the inner basal region (Figs. 2, 4). Parameres long, oval, slightly flattened basally (Figs. 7–11). Guatemala............................................................................ Macrodactylus escuintlaensis Arce-Pérez & Morón

– Length 11.0–13.5 mm, prosternal process non-bifid with rounded apex; protibiae with sparse and slender setae in the inner basal region (Fig. 12). Parameres robust, circular with an internal protuberance near the base (lateral view) (Figs. 21–22); female genitalia (Fig. 23). Mexico and Guatemala.............................. Macrodactylus carrilloi Arce-Pérez & Morón

7 (4) Clypeus elongate (distinctly longer than wide), with lateral margins straight, convergent, and apex nearly straight; black spiniform setae present on the pronotum and elytra in males and females (Fig. 18). Parameres oval, strongly setose (Figs. 39–40). In females, the pronotum has two glabrous, longitudinal lines, abdomen with long setae along midline; pygidium gibbous; genitalia as in Fig. 41. Mexico and Guatemala.................................... Macrodactylus lineatocollis Bates

– Clypeus short, as long as wide, with lateral margins slightly curved, apex concave; males and females without spiniform setae in pronotum and elytra. Females without the above characters in pronotum and elytra................................8

8 (7) Dorsally with dense (long and thick or slender) setae that obscure the coloration of the underlying surface...............9 – Dorsally with fine (slender) setae, not obscuring the color of the surface, or only partly obscuring the elytral surface......10

9 (8) Legs black, dorsally with dense gray or yellow vestiture (Fig. 48). Females with pronotal disc densely covered by erect setae. Male and female genitalia as in Figs. 57–59. Central and southeastern Mexico............. Macrodactylus nigripes Bates

– Legs reddish yellow, dorsally with mustard yellow vestiture (Fig. 17). Female with vestiture only at the sides of the pronotum and without long, erect setae. Male and female genitalia as in Figs. 36–38. El Salvador and Honduras............................................................................... Macrodactylus hondurensis Arce-Pérez & Morón

10 (8) Length approximately 12 mm, elytra and pygidium reddish yellow, elytra with striae feebly indicated (Fig. 20). Parameres circular with a crest on the inner margin and with lateral setae short (Figs. 45–46). Female with pronotal vestiture recumbent; genital plates as in Fig. 47. Mexico, El Salvador, and Honduras............ Macrodactylus montanus Arce-Pérez & Morón

– Length approximately 11 mm, elytra reddish yellow, pygidium black, elytra with distinct striae (Fig. 49). Parameres circular, without a crest, with longer and more abundant lateral setae that M. montanus (Figs. 60–61). Female with pronotal vestiture erect; female genitalia (Fig. 62). Mexico, Guatemala, and Honduras..................... Macrodactylus rufescens Bates

11(1) Elytra glabrous, or with only stout, long, black setae at the base................................................ 12 – Elytra with vestiture uniformly distributed or arranged in longitudinal bands (thick rows)........................... 16

12(11) Elytra bicolored, basal half yellowish orange, distal half iridescent black or dark blue.............................. 13 – Elytra uniformly colored.............................................................................. 14

13 (12) Length 12–13 mm; dorsal surface glabrous; pronotum, basal half of the elytra, and pygidium reddish yellow, distal half of elytra iridescent black or dark blue, scutellum essentially glabrous and same color as adjacent elytral surface (Fig. 15). Male and female genitalia as in Figs. 30–32. Mexico, Guatemala, Belize, and Honduras ….................................................................................................... Macrodactylus dimidiatus Guérin-Méneville

– Length 9–11 mm; pronotum and scutellum setose; pronotum with a well-marked midline extending anteriorly from the base, basal half of the elytra reddish yellow, distal half of elytra and pygidium iridescent black (Fig. 51). Male and female genitalia as in Figs. 66–68. Nicaragua and Costa Rica ………………………………………………….. Macrodactylus sericinus Bates

14 (12) Pronotum and scutellum with yellow vestiture; elytra glabrous, except for stout, long black spiniform setae at base, along the suture, and near scutellum (Fig. 53); prosternal process not visible in most cases. Male and female genitalia (Figs. 72–74). Guatemala, Nicaragua, Costa Rica, and Panama...................................... Macrodactylus sylphis Bates

– Dorsal surface glabrous (and without spiniform setae); prosternal process visible from front…....................... 15

15 (14) Pronotum, elytra, and pygidium similarly colored, yellowish orange (Fig. 54). Male protibia with acute spine in the middle of inner border. Male and female genitalia as in Figs. 75–77. Honduras and Nicaragua................................................................................................... Macrodactylus tibialis Arce-Pérez & Morón

– Pronotum black, elytra and pygidium yellowish orange (Fig. 55). Male protibiae without acute spine in the middle of inner border. Male and female genitalia as in Figs. 78–80. Mexico and Guatemala..................................................................................................... Macrodactylus zaragozai Arce-Pérez & Morón

16 (11) Elytra with short and scale-like, uniformly distributed, yellow setae (Fig. 16). Male and female genitalia (Figs. 33–35). Mexico and Guatemala............................................................... Macrodactylus fulvescens Bates

– Elytra with pale yellow vestiture arranged in longitudinal bands............................................... 17

17 (16) Elytral with greenish yellow or blue sericeous reflections, with one wide longitudinal band of setae along the inner half of disc............................................................................................... 18

– Elytral without sericeous reflections, with at least two longitudinal setose bands.................................. 19

18 (17) Pronotum black with uniformly distributed vestiture, sericeous coloration obscured by vestiture; elytra uniformly colored reddish yellow, with one dense, wide longitudinal setose band on medial half, the lateral half with scattered setae only (Fig. 50). Male and female genitalia as in Figs. 63–65. Guatemala, El Salvador, Honduras, and Nicaragua................................................................................................ Macrodactylus sericeicollis Bates

– Pronotum black with strong greenish yellow or blue sericeous reflections, vestiture yellow on margins and a well-marked midline extending anteriorly from base; elytra bicolored, basal half reddish yellow, distal half dark, iridescent, with one wide longitudinal band in the medial half and two irregular bands on the lateral half (Fig. 52). Male and female genitalia as in Figs. 69–71. Nicaragua, Costa Rica, and Panama........................................... Macrodactylus suavis Bates

19 (17) Elytra with two well-defined longitudinal bands on the interstriae 1 and 3, interstriae 2 and 4 costate (obviously raised), glabrous; often with sublateral rows of setae that appear as bands (Fig. 13). Male and female genitalia as in Figs. 24–26. Mexico to Nicaragua................................................................ Macrodactylus costulatus Bates

– Elytra with three well-defined longitudinal bands, as well as a well-marked sublateral band (Fig. 19); interstriae not costate. Male and female genitalia as in Figs. 42–44. Mexico.................................. Macrodactylus lineatus Bates