Dilychnia propinqua, (OLIVIER, 1909), 2020

DILYCHNIA PROPINQUA ( OLIVIER, 1909) View in CoL COMB. NOV.

( FIGS 5, 14, 16, 19, 33, 34, 36)

Lucidota propinqua Olivier, 1909: 111 View in CoL (desc.); Blackwelder, 1945: 354 (cat.); McDermott, 1966: 68 (cat.).

Type material: Holotype examined, male ( MNHN) ( Fig. 33A). Labels: Brasilien, ex. coll. Frühstofer. [green label]; Lucidota propinqua Ern. Oliv. [light brown label] ( Fig. 33B).

Diagnosis: Antennomere III one-quarter shorter than scape ( Fig. 14G); sterna VI and VII bearing light organs with lateral margin straight and almost reaching the sternal margin ( Fig. 34D); sternum VIII with posterior margin acuminate as long as one-half of sternum height ( Fig. 5E); pygidium with lateral margin rounded and posterior margin with parasagittal indentation and median region rounded ( Fig. 5D); aedeagus parameres with arched projection and phallobase symmetrical with posterior margin with median region rounded ( Fig. 5G).

Colour pattern: Frons black, antenna dark brown, mouthparts dark brown ( Fig. 14); pronotum orange ( Fig. 16); scutellum dark brown ( Fig. 34A); elytron black ( Fig. 19A–C); profemur almost entirely orange, mesofemur orange to half of length and dark brown towards apex, metafemur with basal one-third orange and dark brown towards apex. Tibia and tarsus dark brown ( Fig. 36); sterna II – V dark brown, sterna VI and VII translucent, and sternum VIII with posterior margin dark brown and pygidium black ( Fig. 5).

Head: Antenna filiform, covered with short setae ( Fig. 14G); labrum rounded anteriad, as wide as long ( Fig. 14A); palpi four-segmented: I small, triangular with posterior angles acute in relationship to II; II 2× longer than III, subtriangular; III trapezoidal with margins rounded; and IV securiform, 2.5× longer than II, narrowing abruptly towards apex. Labium with palpi three-segmented: I rectangular; II triangular, 2× longer than I, slightly enlarged towards apex; and III securiform, 1.5× longer than II ( Fig. 14).

Thorax: Pronotum semicircular, one-third wider than long, and anterior, lateral and posterior margins with few punctuations, anterior and lateral margins slightly concave, posterior margin median region with acute projection and posterior angles prominent and acute with apex slightly rounded ( Fig. 16A–D). Hypomera trapezoidal with posterior margin sinuose and laterally rounded ( Fig. 16E). Scutellum rhombus shaped with posterior margin emarginate ( Fig. 34A). Elytra slightly convex with lateral margin rounded ( Fig. 19A–C). Hind wing membranous and well developed, posterior margin sinuose, 2× longer than wide. Subcostal almost reaching the anterior margin; CuA2 absent. MP-Cu present; MP 3 + 4 long, beginning basally; r4 almost as long as RP + MP 1 + 2, almost reaching distal margin, J slightly shorter than RP + MP 1 + 2; r3 as long as half of RC width ( Fig. 19D); metafemur slightly thinner than pro- and mesofemora; tarsomere I of pro- and mesolegs 1.5× longer than II, tarsomere I of metaleg 2× longer than II; pro- and mesotarsomeres with apex indented; II 1.5× longer than III; III subrectangular; claws simple ( Fig. 36).

Abdomen: Sterna with lateral margin divergent posteriad, posterior angles acute ( Fig. 5A–C); sterna VI and VII with complete light organ ( Fig. 34D); sternum VIII slightly wider than long ( Fig. 5E); pygidium slightly wider than long, posterior margin with two parasagittal emarginations, median region rounded and posterior angles projected beyond median region ( Fig. 5D); and sternum IX subtriangular with posterior margin rounded ( Fig. 5F).

Aedeagus: Phallobase posterior margin rounded; parameres sinuose with constriction in apex and strongly mucronate basally ( Fig. 5G); phallus narrowed and extending to half of phallobase length ( Fig. 5H–I).

Female: Metathorax with posterior margin light brown in ventral view; sternum VI with median region with light organ elliptical; sternum VII median region with circular light organ; sternum VIII black with lateral margin slightly sinuous, converging posteriad, and posterior margin with median region slightly emarginate; pygidium posterior margin with posterior angles acute, and median region acuminate.

Remarks: Dilychnia propinqua can be distinguished from others by its colour pattern, its light orange elytron and black pronotum ( Figs 16, 19A–C, 34A), filiform and black antennomeres III –XI with elongate flabellum ( Fig. 14G), sternum VIII with a light brown and acuminate to mucronate posterior margin ( Fig. 5E), pygidium with projected posterior angles ( Fig. 5D) and the male aedeagus with rounded phallobase ( Fig. 5G–I).

This firefly is active from twilight and throughout the first hours after nightfall, constantly flashing during this period and occasionally also during the night. The flashing pattern is composed of three to four reddish orange flashes. We decided to transfer this species to Dilychnia because it shares similarities, such as the acuminate to mucronate sternum VIII; the aedeagus with mucronate basal region of the parameres and a symmetrical phallobase. Our phylogenetic analysis also corroborates this placement.

Material examined: BRAZIL: Rio de Janeiro: Rio de Janeiro, Parque Nacional da Tijuca , Trilha Bom Retiro – Cocanha, 22°56 ′ 96,7 ″ S, 43°17 ′ 67,9 ″ W , 786 m, 2 male, XII.2016, L. Silveira & J. Mermudes, Malaise ( DZRJ) , 1 female, I.2017, L. Silveira & J. Mermudes, Malaise ( DZRJ), Rio de Janeiro, Taquara, Parque Estadual da Pedra Branca , 2 male, 11. II .2017, A. L. Diniz Ferreira, Luz ( DZRJ) , 1 male, 11. II .2018, A. L. Diniz Ferreira, S. Vaz N. Campos ( DZRJ) .

DILYCHNIA DUMASI VAZ, MERMUDES, PAIVA &