Acoma cimarron, Warner, 2011

Warner, William B., 2011, Four new species of Acoma Casey, with a key to species in the genus (Coleoptera: Scarabaeidae: Melolonthinae), Insecta Mundi 2011 (172), pp. 1-17 : 5-6

Acoma cimarron new species

Figures 24-27

Type Material. Holotype male ( UNAM), labeled: “ MEXICO: Sonora: Rancho San Huberto, 2.6 mi. SW. Hwy. 29, Near El Cimarron , 29°22’01”N, 112°04’34”W; elev. 574 ft.; 3-AUG-2009; G. Nogueira & R. Cunningham; at UV ( BL, BLB) and Hg vapor lights set in Sonoran desert scrub.”

Paratypes, (16 males): same as holotype (15); “ Mexico: Sonora; 15 mi. S. Hermosillo; 16-IX-1980; Robert Gordon.”

Paratypes are deposited in GNGC, IEXA, MXAL, RACC, USNM, WBWC.

Diagnosis. Reddish brown, pronotum glabrous except for marginal fimbriae; elytral disc glabrous; frontoclypeal area strongly reticulately sculptured; antenna 9-segmented, with 3-segmented club; anterior tibia tridentate; metatibia with medial carina strongly flared; paramera as in Figure 27 .

Description. Holotype male, length: 8.1 mm, width: 3.5 mm, widest at about middle of elytra.

BODY reddish brown, interpunctural surfaces shiny and micropunctate, hairs lighter colored and contrasting with ground color. HEAD with front and clypeal base scabrously, subreticulately punctaterugose, flattened; clypeus broadly rounded, apical margin more or less arcuate, distinctly reflexed, disc concave, deeply punctate, punctures mostly separated by 1-3 times their own diameters; antenna 9- segmented, club 3-segmented, not quite twice as long as non-club segments together. PRONOTUM glabrous except for marginal bead, length about 0.45 elytral length, widest at about middle; lateral margins slightly diverging to middle, anterior pronotal angles very obtuse, not distinctly drawn forward next to eyes; disc glabrous, moderately densely and distinctly punctate, punctures subcontiguous to mostly separated by about 2-4 times their own widths, midline impunctate and weakly impressed. SCUTELLUM lobiform, with apex broadly rounded, disc densely minutely punctate. ELYTRON with disc glabrous, setae arising only from epipleuron and on base, but not posterior to scutellar apex; strial channels somewhat irregular but distinct, strial punctures distinct, intervals very irregularly uniseriately punctate, punctures distinct, mostly separated by about 1-3 times their own diameters, intervals weakly rugulose. PYGIDIUM longer than broad, subscutelliform, apex arcuate, shagreened and broadly weakly reflexed, disc shiny, midline narrowly mostly impunctate, otherwise distinctly subcontiguously punctate, punctures setigerous. LEGS: Protibia moderately robust, tridentate, apex of basal tooth at about middle; metatibia flaring from base to medial carina which juts shelf-like over abruptly narrower distal section which again flares to apex, with widest corbel diameter slightly more than half pygidial length, posterior tarsal claws over 1/3 length of segment from which they arise. GENITALIA: paramera ( Fig. 27 ) with apices moderately deflexed and ventrobasal emargination comparatively short and distinct.

Variation. Length: 5.9 – 8.5 mm, width: 2.6 – 3.8 mm. Clypeal form varies moderately in shape and length/width proportions, with apex broadly rounded to more or less truncate, but lateral margins are weakly convex in all specimens seen. Body color varies from medium reddish brown to nearly piceous. The protibial basal tooth is submedian in some paratypes, and length of teeth varies because of wear. The metatibia is allometrically shortened with the medial ridge more strongly flaring in proportion to increasing body size. The paratype from 15 miles south of Hermosillo is darker than the others, and has the metatibia even more strongly shortened, but otherwise is similar to paratopotypes.

Etymology. This specific epithet (a noun in apposition) is named for the vicinity of the type locality, as well as for the Mexican big horned sheep ( Ovis canadensis mexicana Merriam ), the “borrego cimarron” characteristic of the area.

Remarks. Both known localities, although about 122 km (76 miles) apart, are on washes that drain to Bahía de Kino; the species is expected to occur along other washes in that drainage.

The combination of 9-segmented antennae with 3-segmented club, glabrous elytral disc, “coffee-colored” body, rounded clypeus, strongly protruding medial metatibial carina, and mainland Mexican distribution make this species easily identifiable. Specimens of A. cimarron imperfectly key to A. glabrata in Howden (1958), but specimens of A. glabrata are very different in color and proportions, have 10-segmented antennae, longer clypeus, tarsi, and antennal club, broader metatibia, and are restricted to deep sand dunes of the Gran Desierto de Altar region of northwestern Sonora, the Algodones dunes in eastern California, and nearby dunes in northeastern Baja California. Except for having 9-segmented antennae, all these differences also apply to A. howdenorum . Additionally, males of A. cimarron have a much more deeply, coarsely sculptured head and wider, more rounded clypeus than males of A. glabrata or A. howdenorum .

Figures

Figure 24-25. Acoma cimarron Warner, holotype: 24) Dorsal habitus. 25) Metatibia.

Figure 26-27. Acoma cimarron Warner: 26) Head. 27) Paramera.