Spintherophyta punctum Gilbert and Clark, 2020

Gilbert, Arthur J. & Clark, Shawn M., 2020, A New Species of Spintherophyta Dejean, 1836 (Coleoptera: Chrysomelidae: Eumolpinae) from the California Channel Islands, USA, The Coleopterists Bulletin 74 (3), pp. 555-562 : 556-559

Spintherophyta punctum Gilbert and Clark , new species

zoobank.org/ urn:lsid:zoobank.org:act:7C0EEB8C-7F7B-4E84-A484-4E2139193BA3 ( Figs. 1–3 , 8–9 )

Diagnosis. Among the United States species, S. punctum most closely resembles S. arizonensis . Using Schultz’ s (1976) key to the Spintherophyta species in America north of Mexico, this new species would be identified as S. arizonensis . The two species are of similar size and coloration, and both have the prosternum recurved ventrally. However, the strongly alutaceous surface and dense, coarse punctation of the pronotum ( Figs. 1–3 ), along with the much more coarsely punctate elytra of S. punctum ( Figs. 1–2 ), will separate the two species. The aedeagus of S. punctum ( Figs. 8–9 ) is similar to that of S. arizonensis in lateral perspective but distinctly different in dorsal view ( Figs. 10–11 ). See the Description and Comments sections below for more detailed information.

Description. Holotype Male. Body, in dorsal view, oval, with pronotum nearly as wide as elytra ( Fig. 1 ); length 3.2 mm; width 2.0 mm. Body, in lateral aspect, with dorsal outline convex, with ventral outline flat ( Fig. 2 ). Head and pronotum alutaceous, bright green; elytra shiny bright blue; venter black; femora dark with greenish luster; tibiae mostly dark with greenish luster, except distal end testaceous; tarsi reddish-brown without luster; antennomeres 1–6 testaceous, 7–11 dark-brown, expanded. Head alutaceous, glabrous, deeply, coarsely punctate ( Fig. 3 ); vertex with punctures separated by width of puncture; frons coarsely punctured, less densely than vertex, with punctures separated by more than width of puncture; clypeus punctured like vertex, widely, shallowly emarginate; frontoclypeal suture obsolete; eyes oblong, nearly twice as long as wide; concave near antennal fossa. Mouthparts enlarged (compared to female), reddishbrown; labrum shallowly concave, with short setae; maxillae and labium with terminal palpomeres attenuate towards apex. Antennae extending to middle of elytron; antennomere 1 about twice as long as broad, glabrous; antennomere 2 about equal in length and width, much narrower and shorter than antennomere 1, glabrous; antennomeres 3–6 sparsely pubescent, subequal in length; antennomeres 7–11 densely covered with very short pubescence and with a few longer setae, each antennomere about as long as broad, about twice as broad as each of antennomeres 2–6; antennomere 11 about as broad as 10, but distinctly longer, attenuate towards apex. Pronotum about twice as wide as long, nearly as wide posteriad as distance across elytral base, arcuately narrowed to anterolateral corners, with anterolateral edge transitioning smoothly with head; anterior edge with minute, smooth marginal bead; posterior edge not margined; lateral edges with distinct, thin, flattened marginal bead; discal surface distinctly alutaceous, densely and deeply punctate, with punctures larger than those of frons or vertex, but smaller than those of elytra; many punctures contiguous, with some tending to be elongated towards lateral margin. Scutellar shield metallic black with greenish luster, equilaterally triangular; surface glabrous, shining, impunctate. Elytra slightly broader at base than posterior portion of prothorax, of uniform width until curving inward towards apex. Humeri prominent. Punctures next to suture large, seriate, separated from each other by distance equal to about half width of puncture; remaining punctures larger, separated by distance less than a quarter width of puncture. Vague costa present along lateral posterior half of each elytron. Interpunctural areas glabrous, shiny. Epipleuron gradually narrowed from base to apex. Ventral areas black, not metallic, glabrous, entirely impunctate, except prosternum. Prosternum coarsely punctate, as wide as a coxa medially, slightly expanded posteriad of coxae, with apical, ventrally projecting lip; front coxal cavities closed. Abdominal ventrites each with one or two long, centrally located setae. Legs with profemur black with greenish luster, except reddishbrown basally. Procoxae pubescent. Tibiae black with greenish luster, except apical tip testaceous. Tarsi reddish-brown; first tarsomere expanded on pro- and mesotarsi, tarsal claws appendiculate. Aedeagus, in dorsal view, broad in basal fourth, narrowed in middle third, broad near distal fourth, with apical fifth gradually narrowed to bluntly pointed tip ( Fig. 8 ). In lateral view, aedeagus evenly curved along entire length, except towards base; distal portion gradually narrowed to acute apex ( Fig. 9 ).

Variation. The color varies from blue to greenish and black. A few specimens appear bicolored, with the elytra blackish or purplish, with the pronotum having a purplish tint. In females, the basal tarsomeres are narrower than in males. The female mandibles are slightly smaller than the male (but not nearly as sexually dimorphic as in the similar genus Metaparia ). The female fifth ventrite has a slightly ventrally curved tip, whereas the fifth ventrite in the male is flat. Male beetles (n = 8) measure 2.8–3.4 mm in length; females (n = 10) measure 2.8–3.5 mm in length.

Specimens Examined. Holotype (male, LACM): “Calif., Santa Rosa Is. / Santa Barbara Co. / Becher’ s Bay / March 31, 1941 / on leaves of willow.” Paratypes: Calif., Santa Rosa Is., Santa Barbara Co., Becher’ s Bay , March 31, 1941, on leaves of willow (2 males, 1 female, AJGC; 1 female, BYUC; 1 male, 1 female, CASC; 1 female, CSCA; 2 females, LACM; 1 female, TAMU); Sta. Rosa I., Santa Barbara Co., Calif., 6-IV-1941, J von Bloeker (1 male, 1 female, AJGC; 1 female, BYUC; 1 female, CSCA; 2 females, LACM; 1 female, TAMU) .

Etymology. The species epithet “ punctum ” is from Latin and means puncture. It refers to the heavily, coarsely punctured elytra and pronotum. No other Mexican or United States species are as coarsely and heavily punctured on the pronotum as S. punctum . Since the epithet is a noun in apposition, it is not necessary that it have gender agreement with the genus.

Plant Association. Eleven of the 18 specimens were collected on leaves of willow ( Salix L., Salicaceae ). One of the Arizona / California species, S. violaceipennis , has also been reported from willow ( Clark et al. 2004).

Comments. The original description of one Mexican species, Spintherophyta hoegei ( Jacoby, 1881) , is close enough to S. punctum to lead to misidentification. Similarities include elytral punctures that are heavy and dense, but not seriate ( Jacoby 1881). However, examination of a syntype of S. hoegei (BMNH) proves that the two species are quite different. Unlike the new species, S. hoegei does not have alutaceous microsculpture on the head and pronotum; the pronotal punctures are not coarse or dense, but are instead separated by more than the width of the punctures, with no indication of elongated punctures along the lateral margins; the legs are reddish (mostly dark in S. punctum ); and all antennomeres are reddish, as opposed to S. punctum where the basal six antennomeres are testaceous and the distal five are reddish brown.

Spintherophyta punctum is similar to S. arizonensis . However, when comparing the two species, three striking features immediately stand out. First, the punctation and microsculpture are different. The pronotum of S. arizonensis is shining in most specimens (of 30 specimens observed, a few had a slightly alutaceous appearance, but the pronotum was still shiny), and the pronotal punctures are dense and separated, rarely contiguous ( Figs. 5, 7 ). The elytra of S. arizonensis are heavily punctate with large punctures, many of which are contiguous ( Figs. 5–6 ). In contrast, the pronotum of S. punctum is strongly alutaceous and very heavily and coarsely punctured ( Figs. 2–3 ), and the elytra are much more coarsely punctured ( Figs. 1–2 ). The abovementioned coarse punctation and alutaceous surfaces are not only diagnostic in comparison to S. arizonensis , but they are also lacking in the other three Spintherophyta species previously known from the United States. Second, the color is different. Without magnification, specimens of S. arizonensis appear black, while S. punctum appears greenish to blue. Under magnification, some specimens of S. arizonensis have a greenish or purplish tint, with the pronotum and elytra of different shades. Under magnification, most specimens of S. punctum remain primarily green or blue, but a couple were nearly black. Third, the genitalia are different. Although Schultz (1976) did not feel that the aedeagus was “exceptionally diagnostic”, his line drawings appear distinctly different from S. punctum for three of the four species. The aedeagus of S. punctum ( Figs. 8–9 ) compared to S. arizonensis ( Figs. 10–11 ) in lateral profile is thicker throughout its length and more uniformly arched.

Figures

Figs. 1–4. Spintherophyta punctum, new species. 1) Dorsal view; 2) Lateral view; 3) Head, frontal view; 4) Lid of original pillbox containing 11 of the specimens.

Figs. 8–9. Spintherophyta punctum, new species, aedeagus. 8) Dorsal view; 9) Lateral view.

Figs. 10–11. Spintherophyta arizonensis, aedeagus. 10) Dorsal view; 11) Lateral view.

Figs. 5–7. Spintherophyta arizonensis. 5) Dorsal view; 6) Lateral view; 7) Head, frontal view.