Dromochorus welderensis, Duran & Herrmann & Roman & Gwiazdowski & Drummond & Hood & Egan, 2019

Duran, Daniel P., Herrmann, David P., Roman, Stephen J., Gwiazdowski, Rodger A., Drummond, Jennifer A., Hood, Glen R. & Egan, Scott P., 2019, Cryptic diversity in the North American Dromochorus tiger beetles (Coleoptera: Carabidae: Cicindelinae): a congruence-based method for species discovery, Zoological Journal of the Linnean Society 186, pp. 250-285 : 275-276

DROMOCHORUS WELDERENSIS DURAN, HERRMANN, ROMAN & EGAN SP. NOV.

( FIGS 8B , 9F )

Common name

Gulf prairie tiger beetle.

Type locality

Welder Wildlife Foundation, Sinton , TX. Holotype (deposited in NMNH): 1 ♂, Texas: San Patricio Co. / Welder Wildlife Foundation / 11-June-2013 /Coll: A. Mitchell . Paratypes: 18 ♂♂, 15 ♀♀, Texas: San Patricio Co./Welder Wildlife Foundation/11-June-2013/ Coll: A. Mitchell. 2 ♂, 2 ♀, Texas/Buckeye - Matagorda Co./6-8-17 // J.D. Mitchell collector (NMNH). 2 ♀, Texas: San Patricio Co./Sinton/14-V-1966 // leg. W.T. Murray (JSC). 2 ♂, Texas, Victoria/VI-2–06 // C.R. Jones collector. 1 ♀, Texas: Dickinson/May 29 // TAMU-ENTO X0898573 (TAMUIC).

1 ♂, 1 ♀, Texas: Bee Co./Pettus/10.V.1964 // Leg. Pryor (SFASU). 4 ♂, 1 ♀, Texas: Nueces Co./Luetgens Coll. (AMNH). 1 ♀, Texas: Corpus Christi/VI-7-1969/ C.W. Griffin // Nueces River Park (NMNH).

Distribution

Found in the Gulf Prairie ecoregion of coastal Texas, from Houston area to Corpus Christi area.

Diagnosis

Dromochorus welderensis is diagnosable by having a black dorsum, often with a faint dark-blue sheen, and no pitting, subsutural foveae or infuscations, in conjunction with all dark maxillary palps and a pronotum with decumbent white setae.

This species is most likely to be confused with D. chaparralensis , belfragei , velutinigrens or minimus .

Dromochorus chaparralensis may be nearly indistinguishable from D. welderensis morphologically, but is ecologically differentiated. The habitat of D. chaparralensis is forested mesquite-chaparral, unlike the Gulf prairie habitat of D. welderensis .

Dromochorus belfragei possesses regular pits on the elytra and often subsutural foveae. Maxillary palpi have a contrasting dark apical segment, with other segments dark yellow-testaceous to dark red-testaceous.

Dromochorus velutinigrens has a very prominent green, blue, or violet dorsal sheen. The body is substantially more narrow and gracile, especially in males. Male D. velutinigrens have an all dark labrum, whereas D. welderensis males possess a pale central spot. Dromochorus velutinigrens have few to no setae on disk of pronotum.

Dromochorus mimimus is generally smaller ( Fig. 6 ; Table 2), and possesses sparse, thin, erect setae on the pronotum. This species also occurs further inland in forested mesquite-chaparral, unlike the Gulf Prairie grassland habitat of D. welderensis .

Description

Medium to large-sized Dromochorus . Body length 10.9– 14.7 mm, mean ♀ 13.7 mm, mean ♂ 12.6 mm. Head slightly wider than pronotum. Head charcoal brownblack with metallic green, green-blue, or bronze

reflections mostly limited to the lateral ridge of the supraorbital region. Fine to marked rugosity often present on the frons and vertex. All head portions glabrous except for two supraorbital setae next to each eye. Frons concave in median area, especially in male, bulging towards slightly convex near anterior margin, clearly delimited from clypeus, gradually blending into vertex. Genae black often with metallic green to violet reflections, with shallow longitudinal striae gradually ending at border of vertex. Clypeus black, with metallic violet to green-coloured reflections. Male labrum tridentate with 6–8 setae, central area pale ochre-testaceous, with a thin, dark-brown to black border posteriorly and sometimes anteriorly, dark-brown to black laterally; in some populations, the pale central area of the labrum may exist as a small spot, up to one-quarter of the total labrum surface; female labrum tridentate with 6–8 setae, entirely dark-brown to black with polished metallic cupreous to green reflections. All segments of maxillary and labial palpi consistently darkbrown; apical segment is not darker than other segments. Antennae normal length, reaching back to humerus and basal third of elytron, slightly longer in male than female; scape dark testaceous to black with metallic reflections of violet, cupreous and green, with 2–3 apical setae; pedicel dark testaceous with metallic reflections of violet, cupreous and green, lacking any setae; flagellum dark testaceous, antennomeres 3–4 with metallic violet and green reflections, densely clothed in short white setae, antennomeres 5–11 dulltextured without metallic reflections and possessing erect setae in apical rings only, covered with fine pubescence throughout.

Thorax: Pronotum 2.6–3.3 mm in length, mean ♀ 3.1 mm, mean ♂ 2.9 mm; width 2.7–3.4 mm, mean ♀ 3.2 mm, mean ♂ 2.9 mm. Pronotum charcoal brown to black, slightly wider than long, widest near anterior margin, width to length ratio 0.9 to 1.1, setae sparse to regular, mostly present along lateral third of dorsal surface; disc finely rugose, with thin but distinct median line, with well-defined shallow sulci present anteriorly and posteriorly; notopleural sutures clearly defined, not visible from dorsal view; proepisternum black, with metallic violet reflections, glabrous. Elytra elongate, dorsal surface convex, 6.3–8.6 mm length, mean ♀ 8.1 mm, mean ♂ 7.4 mm, shape similar in both sexes, but slightly wider in female, especially toward apical third; sutural spine absent, microserrations not present on elytral apices; elytral texture dull, with no pitting present, elytral coloration charcoal brown to black, often with faint blue reflections throughout elytral surface; elytral maculations absent; subsutural foveae absent.

Legs: Pro-, meso- and metacoxae brown to black, with metallic violet to blue reflections, numerous setae on pro- and mesocoxae, sparse on metacoxae; pro- and mesotrochanters with a single erect seta, metatrochanter glabrous, trochanters dark brown-testaceous; femora black with metallic violet reflections, densely clothed in decumbent white setae; tibiae brown, clothed with setae of two types: sparser brown-testaceous long setae and dense, short, decumbent white setae; two tibial spines present; tarsi brown-testaceous, first three dilated protarsomeres in male with dense greyish-white setal pad.

Abdomen: Venter mostly black with metallic olive green and violet reflections. Decumbent setae present on ventrite 1. Ventrites 2–6 have sparse, short, brown erect setae present throughout, but often abraded.

Etymology

Named for the type locality,WelderWildlife Foundation, in Sinton, Texas, as well as the Foundation’s namesake, Robert H. Welder, who established the foundation with the mission to conduct research and education in wildlife management and conservation.

Ecology/natural history

Adults have a long activity period, from mid-May through early August (A. Mitchell, pers. comm.).

Dromochorus welderensis occurs in the Gulf Prairie ecoregion of the Coastal Plain physiographic province of Texas. This Dromochorus is the least associated with tree cover, and D. welderensis is consistently found in tall grasses in upland prairie habitat. Beetles are often found near heavy clayloam or clay banks and hills.

This shade-loving species can be observed in early cool mornings or early evenings, and will try to avoid more open areas on hot, clear days. Even when active, adults are particularly reclusive and tend to stay hidden in tall grasses. They are more reluctant to forage in wide open loam areas, in contrast to D. pruininus and D. velutinigrens . Beetles can also be found on thick grass mats as they forage, mate or disperse. When disturbed, they use these dead grass mats as cover.

Figures

Figure 6. Boxplots, by species, from morphometric data used in principal component analyses (PCA) for each of 411 individuals. PCA indicated three measurements: PC1, overall body length; PC2, shape of the pronotum; and PC3, elytral length to body length ratio, to explain 92–95% of the total variation in the dataset. Shown are targeted comparisons among two main phylogenetic groups: 1, the D. minimus–D. velutinigrens–D. welderensis–chaparralensis group; and 2, the D. knisleyi– D. belfragei–D. pruininus clade. Species labelled with the same letters did not differ significantly from each other, species labelled with ‘ab’ did not differ between other species which were significantly different. Percentages are relative contributions per analyses, and group; outliers are shown as black dots.

Figure 8. A, Elytra showing distinct punctures (foveae) running parallel to the suture of the elytra (D. knisleyi sp. nov.). B, lack of distinct subsutural foveae (D. welderensis sp. nov.).

Figure 9. Dorsal habitus for species of Dromochorus. A, D.pruininus; B, D.belfragei; C, D. knisleyi sp. nov.; D, D. minimus sp. nov.; E, D. chaparralensis sp. nov.; F, D. welderensis sp. nov.; G, D. velutinigrens; H, D. pilatei.