Acoma howdenorum, 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 : 3-4

Acoma howdenorum new species

Figures 6, 7

Type Material. Holotype male ( FSCA): “Ariz: Yuma Co., Mohawk Dunes, ca. 1 mi. S. I-8; v-14-1988; U.V. light; W.B.Warner.”

Paratypes, (193 males) with data: same as holotype (33); “ USA. AZ: Yuma Co., 10 km E. Tacna , Mohawk Dunes, 23 vii.1992, H. & A. Howden ” (6) ; same except: “ 10 mi. E of Tacna ; 32 o 41’N, 113 o 47’; vii.23.1992;UV, W.Warner ” (11) ; same except: “ 32 o 41’45”N, 113 o 47’22”, June 4, 2010 ; UV; W.B.Warner ” (143). (All paratype locality data refer to the same location.)

Paratypes are deposited at ASUT, BCRC, BDGC, CSCA, EMEC, FSCA, CMNC, MJPC, NAUF, PHSC, RACC, RLWE, UAIC, UCRC, UNAM, UNSM, USNM, WBWC.

Diagnosis. Pale testaceous, pronotum and elytra subtransparent (when fresh) and glabrous except for marginal fimbrae and scattered long hairs at elytral base; clypeal disc nearly impunctate; antenna 9- segmented, with 3-segmented club; anterior tibia tridentate.

Description. Holotype male, length: 5.7 mm, width: 2.5 mm, widest at about middle of elytra.

BODY light testaceous, integument translucent to subtransparent, shiny on head, slightly sericeous on pronotum and elytra. HEAD with front and clypeal base scabrously, reticulately punctate; clypeus subhemihexagonal, margins moderately reflexed, more strongly so apically, disc sparsely, shallowly, finely punctate, punctures separated by about 2 to 6 times their own diameters; antenna 9-segmented, club 3-segmented, segment immediately proximal to club anteriorly prolonged into short lamina. PRONOTUM glabrous except for marginal bead, length about 0.4 times elytral length, widest at about middle; anterior margin weakly bisinuate; posterior margin convex, lateral margins subparallel in about basal half, in apical half straight and converging to slightly obtuse anterior angles which are not drawn forward next to eyes; posterior angles rounded; disk weakly, but moderately punctate, punctures mostly separated by 2 to 4 times their own widths, longitudinal midline very slightly impressed and impunctate. SCUTELLUM lobiform, with apex evenly arcuate. ELYTRON glabrous, weakly striate, striae obsolescent basally, weakly contiguously punctate on disc; intervals more coarsely and distinctly punctate than pronotal disc, but punctures similarly separated. PYGIDIUM with apex broadly arcuate, disc shallowly subcontiguously punctate, punctures setigerous. LEGS: Anterior tibia narrow, gracile, tridentate, basal tooth weak; metatibia rather narrow, widest corbel diameter distinctly less than half pygidial length, posterior tarsal claws about 1/3 length of segment from which they arise. GENITALIA: paramera only weakly and arcuately deflexed in apical third, ventrobasal emargination shallow, moderately long.

Variation. Length: 4.2 – 6.0 mm, width: 1.8 – 2.9 mm. Clypeal shape varies occasionally to subsemicircular, and occasional paratypes have the apical clypeal margin vaguely concave. A few paratypes had one antenna 8-segmented because of fusion in the funicular segments.

Etymology. I take pleasure in naming this species for Henry and Anne Howden, both in recognition of their many contributions to coleopterology and for their help in collecting part of the type series.

Remarks. This species was treated as “variation” within Acoma glabrata Cazier by Cazier (1953), who listed four specimens from Welton and Dome, Arizona; but he purposely excluded them from the paratype series. Howden (1958) followed that lead, quoting Cazier’s (1953) comments on variation. Acoma howdenorum is indeed similar to A. glabrata ; however, A. howdenorum is separated both geographically and phenotypically from that species. It can immediately be differentiated from A. glabrata by its 9- segmented antennae, generally smaller size, less robust tarsi, more gracile tarsi and anterior tibia, differently shaped pronotum and clypeus, more rounded scutellar apex, and thinner integument. Acoma glabrata has 10-segmented antennae ( Fig. 8, 9 ), although occasional specimens may have one antenna with one or more segments partially to completely fused. In all specimens examined (more than 100), however, at least one of the antennae is 10-segmented. Acoma glabrata ranges from the type locality at San Felipe, northward into the Algodones Dunes in SE California. It also occurs in dunes of the Gran Desierto de Altar in northwest Sonora, with its northern terminus in the Yuma Desert in extreme SW Arizona west of the Tinajas Altas and Gila mountain ranges. Acoma howdenorum occurs only to the east of those two mountain ranges in the Mohawk Dune field just west of the Mohawk Mountains, and associated small dunes in the Mohawk Valley near Welton and Dome, where it is sympatric with the southwestern form of Acoma arizonica Brown. Apparently A. howdenorum does not occur on the east side of the Mohawk Mountains as concurrent collecting on a dune field just south of Dateland, AZ, only produced A. arizonica .

Both A. glabrata and A. howdenorum appear to be restricted to deep eolian sand dunes. Specimens of A. glabrata from the USA tend to be rather uniform in size (mostly 6-7 mm long), whereas specimens from the type locality vary widely in size, with some specimens much larger than those from the USA. The Arizona specimens of A. glabrata from south of Yuma differ slightly from specimens collected on the Algodones Dunes (across the Colorado River) as well, but do have 10 segmented antennae and the other differences from A. howdenorum noted above. Acoma glabrata ’s type locality dunes are remote from the Sonoran and US localities, and further study may indicate that the three populations (type locality, Algodones Dunes, Gran Desierto) represent separate species or subspecies. A specimen from the Algodones Dunes in California is shown in Figures 1 , 8 , and 9.

Figures

Figure 6-9. Acoma spp. 6-7) Acoma howdenorum Warner: 6) Dorsal habitus. 7) Antenna. 8-9) Acoma glabrata Cazier (specimen from Algodones Dunes): 8) Dorsal habitus. 9) Antenna.

Figure 1-5. Acoma spp. 1) Acoma glabrata Cazier, head and pronotum. 2-5) Acoma westcotti Warner: 2) Head and pronotum, 3) Dorsal habitus. 4) Left anterior tibia. 5) Pygidium.