Bembidion elescarabajo, Maddison, 2023

Maddison, David R., 2023, A New Subgenus of Bembidion Latreille from México and Guatemala, with Descriptions of Two New Species (Coleoptera: Carabidae), Proceedings of the California Academy of Sciences 67 (19), pp. 433-450 : 443-445

Bembidion elescarabajo , sp. nov.

( Figures 1C , 5C, 5D , 6B )

Holotype male, in UASM, labeled “ MEX. Oaxaca Rte. 175. 28 mi. s. Valle Nacional. 2040 m. Aug. 25, 1974 ” [handwritten], “MIDDLE AMER. EXP. 1974, H. Frania & G.E. Ball collectors”, “David R. Maddison V101490 Voucher Specimen”, “HOLOTYPE Bembidion elescarabajo David R. Maddison [partly handwritten, on red paper]”, “ UASM# 410000 ” [printed on white paper]. Genitalia mounted in Euparal in between coverslips pinned with specimen.

Paratypes (6 males, 6 females). “ Mexico: Oaxaca. 27.5 mi s. Valle Nacional. 5600’ VIII.15 - 16.65”, “ George E. Ball and D.R. Whitehead collectors” (2: UASM, CTVR) . “ MEXICO: Oaxaca. 27.5 mi s. Valle Nacional. 5600’ V.4 -5.1966”, “ George E. Ball and D.R. Whitehead collectors” (5: UASM, UNAM, OSAC, NHMUK, NMNH) . “ MEXICO Oaxaca 36.2 km s. Valle Nacional, Rte. 175 cloud forest ca. 2010 m., April 27, 1977 ”, “MEXICAN EXP. 1977 J.S. Ashe, H.E. Frania, D. Shpeley coll.” (1: UASM) . “ MEX. Oaxaca Rte. 175. 28 mi. s. Valle Nacional. 2040 m. Aug. 28, 1974 ”, “MIDDLE AMER. EXP. 1974, H. Frania & G.E. Ball collectors” (1: UASM) . “ MEX. Oaxaca 35.1 mi. n. Istlan de Juarez, Rte. 175. 2050m, 22.07.1975 ”, “MEX. EXP. 1975, H. Frania & G.E. Ball collectors” (3: UASM, UNAM, OSAC) .

Type locality. México: Oaxaca: 28 miles (45 km) south of Valle Nacional (San Juan Bautista Valle Nacional) along route 175; this is approximately 17.594°N 96.427°W .

Derivation of specific epithet. This species is named in honor of George Ball’s three El Escarabajo campers. George and his colleagues used those trusty vehicles to explore the regions of México inhabited by Geocosmius , and on these journeys most known specimens of the subgenus were collected, including the type series of this species. The name is to be treated as a noun in apposition.

Description. Body length 3.25–3.90 mm. Body brown, with head and pronotum slightly darker than elytra. Legs uniform in color, testaceous or slightly infuscated; antennomere 1 testaceous, antennomeres 2 and 3 with distal half slightly infuscated, remaining antennomeres slightly infuscated; penultimate maxillary palpomere infuscated, antepenultimate testaceous. Mentum with anterior lateral regions large, triangular; medial tooth triangular with rounded tip; frontal furrows weakly defined, somewhat rugose; eyes not prominent; prothorax with greatest width in front of middle; sides sinuate, with sides in front of hind angle straight; hind angle approximately right; posterolateral carina evident, moderately long, and straight; posterior region of pronotum slightly rugose with poorly defined punctures. Elytra with lateral bead not prolonged medially at shoulder; inner three striae well-defined around ed3; striae 4 and 5 faint, even anteriorly, with striae 6 and 7 extremely faint; only first stria evident to apex, with other striae more or less absent from apical fourth. Microsculpture absent from dorsal surface of head at center and from pronotal disc; evident in both sexes over entire surface of elytra, nearly isodiametric (Fig. 6B). Pronotum with two lateral setae on each side; elytron with two setae in third stria. Aedeagus (Fig. 5C, D) similar to members of the nahuala group (Fig. 5A, B, E, F, G), but with ventral margin of the large central sclerite less abruptly bent.

Additional characteristics. All thirteen specimens examined lack hind wings.

Geographic distribution. Known only from four closely proximate localities in Oaxaca along route 175 between San Juan Bautista Valle Nacional and Ixtlán de Juárez, between about 17.604°N 96.381°W and 17.594°N 96.460°W (Fig. 2, star). These localities are at most 9 km apart.

Geographic relationships with other species. One specimen of a nahuala -group species (perhaps Bembidion “Chiapas”) was collected at the same place and time as five of the paratypes of B. elescarabajo: “Mexico: Oaxaca. 27.5 mi s. Valle Nacional. 5600’ VIII.15-16.65”.

Habitat. Based upon imagery in Google Earth, and the annotation “cloud forest” on the label of the 1977 specimen, the known localities are all in cloud forest.

Figures

FIGURE 1. Habitus of Geocosmius species. (A) Bembidion “Chiapas”, brachypterous form, voucher V101274. (B) B. “Chiapas”, fully winged form, voucher V101273. (C) B. elescarabajo, paratype, voucher V101491. (D) B. franiae, specimen UASM371160. Note: B. nahuala (not shown) is extremely similar externally to B. “Chiapas”. Scale bar 1 mm.

FIGURE 5. Aedeagi of Geocosmius. (A) Bembidion “Chiapas”, voucher DNA5317. (B) B. “Chiapas”, voucher DNA4882.Arrow indicates the prominent ridge characteristic of this species. (C) B. elescarabajo, voucher V101490.Arrow indicates the less curved sclerite margin characteristic of this species. (D) B. elescarabajo, voucher V101489. (E) B. nahuala voucher DNA5033. (F) B. nahuala voucher DNA5034. (G) B. nahuala, holotype. (H) B. franiae, voucher DNA4623. Scale bar 100 µm.

FIGURE 6. Microsculpture of Geocosmius. (A) Bembidion franiae, vouch- er DNA4623, (B) B. elescarabajo, voucher V101491. Scale bar 100 µm.