Bembidion cachagua Maddison 2023, sp. nov.
Creators: name: Maddison, David R.
Publisher: name: Zenodo
Year: 2023
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Carabidae
Bembidion
Bembidion cachagua

description: Bembidion cachagua, sp. nov.
(Figures 7, 8)
Holotype male, in CAS, labeled: “ U.S.A.: CALIFORNIA: Monterey Co., Hastings Nat. History Reserve. J.M. Linsdale Colln.”, “C.A.S. Accession 29-V-48 Cachagua Creek”, “David R. Maddison DNA3842 DNA Voucher” [pale green paper], “HOLOTYPE Bembidion cachagua David R. Maddison” [partly handwritten, on red paper]. Genitalia mounted in Euparal in between coverslips pinned with specimen; extracted DNA stored separately.
Paratypes (2 males, 4 females). Same data as holotype (3: CAS, OSAC). “ Pinnacles Nat’l Mon. 4.19.58 Toschi ” (1: EMEC; this is D.R. Maddison DNA voucher number 4758, and EMEC specimen number 348099). “Santa Barbara Cal. May ’91 L.E.R.” (1: MCZ, Hayward Collection). “S. Cal.” (1: UIUC).
Type locality. Cachagua Creek does not flow through Hastings Natural History Reserve, although a tributary, Finch Creek, does. At its nearest Cachagua Creek is approximately 2.7 km from the boundary of the Reserve. It is reasonable to presume that the upper label on the holotype, “ U.S.A.: CALIFORNIA: Monterey Co., Hastings Nat. History Reserve. J.M. Linsdale Colln. ”, was a generic label used for all specimens from the Linsdale collection, as J.M. Linsdale was the Director of the Hastings Natural History Reserve at the time (Alagona, 2012). The lower label presumably allowed customization for each specimen, and the locality information on the second label is thus likely more accurate. Thus, the type locality would more accurately be stated to be “Cachagua Creek near Hastings Natural History Reserve”.
Derivation of specific epithet. Named after Cachagua Creek, the locality at which four of the seven known specimens were found. Treated as a noun in apposition.
Description. Body length 3.45–3.90 mm. Forebody dark brown or piceous, with metallic greenish-yellow or brassy sheen; elytra pale chestnut brown, with the four testaceous elytral spots contrasting only slightly against the ground color (Fig. 7). In four specimens, the antennae are infuscated throughout; in the other three specimens, two of which appear to be teneral, the basal 2.5 antennomeres are testaceous; legs pale reddish brown, slightly infuscated. Frontal furrows shallow, not prolonged onto clypeus. Mentum with anterior lateral regions triangular, large; central tooth of mentum triangular, slightly rounded. Prothorax narrow, only slightly wider than head; hind angles slightly obtuse; posterolateral carina of pronotum long and more or less straight; posterior region of pronotum rugose, wrinkled and with evident punctures (Fig. 7). Elytra with lateral bead not prolonged medially at shoulder; striae shallow, poorly defined, with extremely small punctures. Microsculpture evident throughout the dorsal surface of the forebody in most specimens, more or less isodiametric or slightly transversely stretched, in some specimens effaced in the center of the head between the eyes, and in the center of the pronotal disc; microsculpture effaced from most of elytra, but evident behind the second dorsal discal seta (ed5) as defined, slightly transverse sculpticells. Pronotum with two lateral setae on each side; elytron with two setae in third stria. Aedeagus (Fig. 8) with a small brush sclerite similar to that of B. horni, but with a long, slightly curved flagellum, most similar to that of B. festivum.
Most easily distinguished from other Liocosmius by the stronger and more widespread microsculpture, the greenishyellow metallic sheen on the dorsal surface, and the relatively low-contrast pattern on the elytra. In comparison to Bembidion horni in particular, the pronotum in B. cachagua is much narrower, with straighter sides.
Variation. Some specimens have numerous punctures on the dorsal surface of the head and in anterior regions of the pronotum.
Geographic Distribution. Known only from California from Monterey and San Benito Counties south to Santa Barbara County (Fig. 9).
Geographic relationships with other species. Found sympatrically with four other species of subgenus Liocosmius: Bembidion horni, B. mundum, B. darlingtonielum, and B. festivum.
Habitat. Unknown. It may occur in similar habitats as other Liocosmius, that is, on sandy shores of creeks, most often in shaded or partly shaded areas, and in general where the sand banks are relatively steep.
Notes. I have seen no specimens of this species collected since 1958. In late April and early May 2014, John Sproul and I searched at multiple known localities for this species, including at Hastings Natural History Reserve, Pinnacles National Park, around Santa Barbara, and at many other localities in between. We searched in typical Liocosmius microhabitats (including steep sand banks in partial shade), with no success. Along Finch Creek in Hastings Natural History Reserve, the only Bembidion in those microhabitats was B. iridescens LeConte; in nearby microhabitats along the creek shore were three species of Bembidion: B. californicum Hayward, B. perspicuum LeConte, and B. lugubre LeConte.
description: Published as part of Maddison, David R., 2023, A New Subgenus of Bembidion Latreille from México and Guatemala, with Descriptions of Two New Species (Coleoptera: Carabidae), pp. 433-450 in Proceedings of the California Academy of Sciences 67 (19) on pages 446-447, DOI: 10.5281/zenodo.11067242