Horismenus dennoi Hansson & Kenyon & Benrey 2019, sp. nov.

Figs 17–21, 25–29, 35, 38, 41

Diagnosis. Antennal scrobes join below frontal suture (Figs 25, 26); female flagellomeres comparatively short (Fig. 18), e.g. 1 st flagellomere 2.2× as long as wide; forewing speculum open below; scutellum convex (Fig. 28); first gastral tergite with punctures in posterior ½. Similar to H. butcheri but differs in both sexes in having lateral margin of anterolateral foveae straight (Fig. 38), and with male vertex and thoracic dorsum golden-red (Fig. 21). Also similar to H. multistriatus but differs in same character as mentioned for H. butcheri, and in having anterolateral foveae of propodeum reticulate (Fig. 38).

Description. FEMALE. Length 2.7–2.8 mm. Scape yellowish-white with apical ¼ dark brown with metallic tinges; pedicel and flagellum metallic bluish-green. Frons and vertex metallic bluish-green. Mesoscutum and scutellum metallic bluish-green, propodeum with smooth parts golden-green, reticulate parts metallic dark purple. Coxae metallic bluish-green; femora, tibiae and tarsi yellowish-white. Wings hyaline. Petiole metallic dark purple. Gaster with first tergite with anterior ¼ golden-green, posterior ¾ metallic dark purple; remaining tergites metallic dark purple.

Antenna as in Fig. 18. Frons with interscrobal area smooth, clypeal area and part just above frontal suture with raised and weak reticulation, remaining parts with raised and strong reticulation; frontal suture V-shaped, incomplete not reaching eyes; antennal scrobes join below frontal suture. Vertex with engraved and strong reticulation; with a median groove in posterior part, groove continues down on occiput. Occipital margin rounded.

Mesoscutum with raised and strong reticulation; notauli as narrow and distinct grooves. Scutellum with engraved and strong reticulation. Dorsellum smooth, anterolaterally with two large foveae. Coxae smooth and shiny. Propodeum smooth and shiny, posterolateral parts, submedian grooves and anterolateral foveae reticulate; propodeal callus with two setae. Forewing speculum open below; with 16–20 admarginal setae.

Gaster with first tergite smooth and shiny in anterior ½ and along posterior margin, posterior ½ with punctures.

Ratios. DE/DO 4.1; WH/DE 2.6; HE/MS/WM 4.6/1.0/2.7; POL/OOL/POO 4.8/1.2/1.0; WH/WT 1.1; LW/ LM/HW 1.9/1.1/1.0; PM/ST 1.2; LC/WC 8.3; WG/WC 2.8; LS/LT 0.17; LP/WP 1.1; MM/LG 1.0.

MALE. Length 2.1–2.2 mm. Vertex and thoracic dorsum golden-red. Colour otherwise as in female. Antenna as in Fig. 19. Head and mesosoma as in female.

Ratios. HE/MS/WM 4.2/1.0/2.4; LP/WP 1.4; MM/LG 1.6.

Distribution. Mexico.

Hosts. Acanthoscelides sp. (Coleoptera: Chrysomelidae: Bruchinae) on Phaseolus vulgaris (Fabaceae).

Type material. Holotype female labelled “ MEXICO, Morelos, Cuernavaca, 99°13'03.0''W 18°58'41.9''N, 1884 m, 21.xii.2007, S. Kenyon ”, “From Acanthoscelides sp. on Phaseolus vulgaris ”, in MZLU. Paratypes: 15♀ 17♂ mounted on cards (in MZLU). MEXICO. Mexico: Jalmalonga, 99°29'23.3''W, 18°54'54.1''N, 1527 m, 20.xii.2009, I. Zaugg, from Acanthoscelides sp. on Phaseolus vulgaris (1♀ 2♂). Michoacan: Ario de Rosales, 101°44'17.2''W 19°11'57.9''N, 1716 m, 29.xii.2009, I. Zaugg, from Acanthoscelides sp. on Phaseolus vulgaris (1♀); Morelos: with same label data as holotype (3♀ 1♂); from same locality and same host as holotype but collected 6.i.2008 (4♀ 1♂), 25.1.2008 (4♀ 3♂), 23.ii.2008 (1♀); Cuernavaca, 99°13'02.1''W 18°58'41.4''N, 1862 m, 10.xii.2009, I. Zaugg, from Acanthoscelides sp. on Phaseolus vulgaris (1♂); Cuernavaca, 99°12'34.8''W 18°58'53.8''N, 1886 m, 22.xii.2009, I. Zaugg, from Acanthoscelides sp. on Phaseolus vulgaris (2♂), and from same locality and same host but collected 14.i.2010 (2♀ 4♂); Tepoztlan, 99°07'08.1''W 18°59'50.7''N, 1908 m, 6.i.2008, S. Kenyon, from Acanthoscelides sp. on Phaseolus vulgaris (1♂), and from same locality but collected 25.i.2008 (1♂).

Etymology. This species is named after Robert F. Denno in recognition for his significant contributions to insect ecology.

Molecular data. Horismenus dennoi equals “HB2” in Kenyon et al. (2015) and molecular data associated with “HB2” is accounted for in that paper.