Petalacmis triplehorni Silveira & Branham, 2022

Lima da Silveira, Luiz F. & Branham, Marc A., 2022, A new species of Petalacmis firefly from Bolivia, with a key to species (Coleoptera, Lampyridae), ZooKeys 1092, pp. 63-77 : 63

Petalacmis triplehorni Silveira & Branham sp. nov.

Figs 1 , 2 , 3 , 4

Diagnosis.

The three species of Petalacmis are easily diagnosable by size (Table 1 ), along with the morphology of antennae, elytra, and pygidium (see key below). Petalacmis triplehorni sp. nov. can be identified by the following combination of characters: antennomeres V and VII slightly longer and wider than adjacent antennomeres (Fig. 2H-I ), elytron subparallel-sided (Fig. 3L ), pygidium with sides divergent to basal third, then convergent apically with almost straight margins, posterior margin slightly bisinuose, lateral thirds subequal to or slightly longer than median third (Fig. 4A, C ). Measurements are given in Table 1 .

Description of male.

Color pattern: overall brown, except for the dark brown pronotal disc, translucent parasagittal rounded spots on pronotal expansions, and translucent sterna VI-VIII (Fig. 1 ); pronotal expansions often light brown (Suppl. material 1: Fig. S1).

Head: head capsule about 1/3 × wider than long, posterior margin almost straight, except for the dorsal margin of occiput, which is rounded (see dorsal view, Fig. 2A ), slightly taller than long (Fig. 2D ), vertex slightly depressed between the eyes (Fig. 2E ). Frons slightly intumescent (Fig. 2D ), antennal sockets elliptical, 2 × taller than wide, obliquely disposed, as wide as 1/3 eye; antennifer process barely visible (Fig. 2C ). Eye as wide as 1/3 head width in dorsal view (Fig. 2A ), 2/5 in ventral view (Fig. 2B ), dorsal margin emarginated inwards (Fig. 2A ), frontal inner margin rounded, strongly convergent ventrally (Fig. 2B ), almost occupying the whole head capsule in lateral view (Fig. 2D ), indented posteriorly (Fig. 2B, D ). Antenna with nine antennomeres (Fig. 2H, I ); scape slightly longer than wide, basally constricted; pedicel basally constricted, slightly wider than long, 1/2 as long as scape; antennomeres III-VIII transverse, progressively compressed, with decumbent bristles, subequal in length, except for V and VII, which are slightly longer and wider than neighboring antennomeres, IX petal-shaped, lateral margins asymmetrical (Fig. 2H ); frontoclypeus strongly depressed between antennal sockets and labrum (Fig. 2C ). Labrum (Fig. 2A-C ) subcircular, slightly acuminate anteriorly, connate to frontoclypeus, slightly wider than antennal socket. Mandibles short (as long as labrum), slightly curved, apically obtuse, homogeneously bristled (Fig. 2A, D ). Maxilla (Fig. 2B, C ) with cardo well sclerotized, rectangular; stipes oblong, subtriangular in ventral view, internal margin slightly curved, posterior margins rounded, palp with 4 palpomeres; II-IV subcylindrical and transverse, II longer than I and as long as palpifer, I as long as III, III transverse; IV lanceolate, 3 × longer than III, with apical margin covered with bristles. Labium (Fig. 2B ) with mentum membranous and barely distinct, divided sagittally forming two plates, each plate elongate; submentum membranous and indistinct; palp with 2 distinct palpomeres, apical palpomere obconical. Gula coriaceous, as long as wide, paired tentorial pits conspicuous. Occiput subtriangular, maximum width slightly over 1/2 head width, anterior margin slightly sinuose (Fig. 2E ).

Thorax: pronotum with anterior margin slightly sinuose and acuminate anteriorly (Fig. 3A ), lateral margins slightly rounded to subparallel, posterior angles somewhat acute but not pointed, posterior margin almost straight, slightly rounded by the disc; disc subquadrate (Fig. 3A ), slightly depressed by posterior half (in lateral view, Fig. 3E ), regularly punctured, punctures small and bristled, evenly spaced about 2 × puncture size; without a distinct line of deeper marginal punctures; pronotal expansions well developed, anterior expansion convex in lateral view (Fig. 3C, E ), maximal length almost as long as disc (Fig. 3A ); posterior margin about as wide as distance between elytral humeri (Fig. 1A ); lateral expansions bent upwards in posterior view (Fig. 3D ). Hypomeron slightly over 2 × longer than tall, with a well-delimited posterior angle (Fig. 3E ). Prosternum smallest length about 10 × as wide as its greatest length (Fig. 3B ). Proendosternite apically acute, widely divergent, as long as core prosternum smallest length (Fig. 3D ). Mesoscutellum very short (Fig. 3F ), with posterior margin pointed, normally at a lower level than elytra (Fig. 1A ). Elytron (Fig. 3L, M ) subparallel-sided, almost 5 × longer than wide, pubescent, secondary pubescence absent, with shallow irregular punctures, texturized, with evanescent 4 costae, marginal costa narrow, epipleuron reaching basal ¼. Hind wing well developed (Fig. 3N ), posterior margin with anal embayment (sensu Lawrence et al. 2021), slightly less than 2 × wider than long, r4 3 × longer than r3, radial cell 3 × wider than long, distant from anterior margin more than the caliper of RA, costal row of setae conspicuous (Fig. 3N ); CuA1 cross vein evanescent, CuA3+4 cross vein absent; radial cell, r3 and r4 evanescent, veins posterior to MP progressively evanescent from apex to base.

Alinotum overall weakly sclerotized, slightly wider than long (Fig. 3G ), lateral margins convergent posteriorly, posterior margin slightly emarginate; prescutum extending up to half metascutum length; without a distinct rounded area, scutum-prescutal plates distinct and extending ridges to half alinotum length; metascutellum glabrous, with lateral margins subparallel-sided, scutum-scutellar ridge strongly divergent posteriorly. Mesosternum weakly sclerotized, posterior margin medially rounded (Fig. 3H ). Mesosternum-mesepisternum suture barely visible (Fig. 3H ). Mesepisternum-mesepimeron suture conspicuous (Fig. 3H ). Mesepimeron-metasternum suture coriaceous (Fig. 3H, I ). Metasternum strongly depressed by mesocoxae, without a distinct anterior medial keel, discrimen reaching basal 1/3 of metasternum length, lateral margins divergent posteriorly up to outermost part of metacoxa, then convergent posteriorly, posterior margin bisinuose (Fig. 3H-I ). Metepisternum almost 3 × longer than tall Fig. (3K). Profemur about as long as protibia; meso and metatibia of about the same length and slightly longer than protibia (Fig. 3O ). All legs lacking tibial spurs, with tarsomeres progressively shorter up to IV, which is bilobated, lobes reaching ½ V length, V slightly shorter than I, and with simple, untoothed claws (Fig. 3O, P ). Mesendosternum with 2 parasagittal projections slightly directed outwards, irregularly alate (Fig. 3I-K ). Metendosternum spatulate, roughly rhomboid (about as long as wide, with 2 acute lateral laminae), anteriorly indented (Fig. 3I ).

Abdomen: tergum I with laterotergite membranous, roughly triangular, almost indistinct (Fig. 3K ); spiracle elliptical, obliquely attached to thorax (Fig. 3G, K ). Posterior corners of terga I-III almost right-angled, IV slightly projected, V-VII rounded and progressively projected and acute (Fig. 4A-C ). Sterna II-IX visible (Figs 1B , 4C ), V distinctly more sclerotized than neighboring sterna, VI and VII with well-developed, transverse light organs, almost as long and wide as sterna (Fig. 4B, C , Suppl. material 1: Fig. S1). Spiracles ventral, at mid-length (Fig. 4B, C ). Sternum VIII with posterior margin slightly emarginate (Fig. 4B, C ). Pygidium with anterior margin strongly emarginate, lateral margins almost straight and convergent posteriorly, posterior margin bisinuate, lateral thirds subequal to or slightly longer than median third (Fig. 4C ). Syntergite membranous, as long as 4/5 sternum IX length, widely connate to sternum IX, without distinct sutures, posteriorly bristled, anterior margin slightly emarginate (Fig. 4D-F ). Sternum IX symmetric, medially divided by a membranous line, anterior margin rounded, lateral margins strongly convergent anteriorly (Fig. 4D-F ). Aedeagus overall well sclerotized (Fig. 4G-J ). Phallus (Fig. 4G-I ) with a well-sclerotized dorsal plate, ventral plate indistinct; dorsal plate basally connate to parameres, curved dorsally, apically truncate, deeply excavate ventrally (Fig. 4G ), without apical lobes or arrow-shaped structures. Parameres ventrally projected basally, projection somewhat rounded; reaching the dorsal plate of phallus length, with typical lampyrine inner lobes but coriaceous; with an apical pointed projection, which is membranous.

Female and immature stages.

Unknown.

Etymology.

This species is named for Dr Charles “Chuck” Triplehorn, Professor Emeritus of the Ohio State University, who collected the first specimens of Petalacmis praeclarus that one of us (MAB) first encountered as a graduate student while investigating the systematics of the family Lampyridae . Dr Triplehorn has been both a mentor and an inspiration to MAB. It is with great appreciation and respect for Dr Triplehorn that we name this species after him.

Material examined.

Holotype, male. Bolivia: Santa Cruz, Potrerillo del Guenda Reserve , 1322' elev., 17°40.262'S, 63°27.445'W, at light, J. McHugh lab exped. leg., 6-12-I-2005 (ANCB).

Paratypes (n = 14). Bolivia • Santa Cruz, Potrerillo del Guenda Reserve. ; 1322' elev.; 17°40.262'S, 63°27.445'W; at light; J. McHugh lab exped. leg.; 6-12-I-2005 (1 ♂, USNM) • Santa Cruz, 3.7 km SSE of Buena Vista, Hotel Flora and Fauna ; 405 m elev.; 5-15-XI-2001; 17°29.949'S, 63°33.152'W; M.C. Thomas & B.K. Dozier leg.; tropical transition forest (3 ♂, FSCA) • idem. (2 ♂, ANCB) ; Santa Cruz, 3.7 km SSE of Buena Vista, Hotel Flora and Fauna ; 405 m elev.; 5-15-XI-2001, 17°29.949'S, 63°33.152'W; M.C. Thomas & B.K. Dozier leg.; tropical transition forest (1 ♂, OSUC) • Santa Cruz, 3.7 km SSE of Buena Vista, Hotel Flora and Fauna ; 405 m elev.; 5-15-XI-2001; 17°29.949'S, 63°33.152'W; M.C. Thomas & B.K. Dozier leg.; tropical transition forest, blacklight trap (2 ♂, UGCA) • Santa Cruz, 3.7 km SSE of Buena Vista, Hotel Flora and Fauna ; 430 m elev.; 2-13-III-2000; M.C. Thomas leg.; tropical transition forest (3 ♂, ANCB) • Santa Cruz, 3.7 km SSE of Buena Vista, Hotel Flora and Fauna ; 430 m elev.; 14-19-X-2000; M.C. Thomas leg.; tropical transition forest (1 ♂, ANCB) • Santa Cruz, 40 km NW of Potrerillo del Guenda ; 400 m elev.; Gino Nearns leg., 17-XII-2004 (1 male, USNM) .

Figures

Figure 1. Habiti of Petalacmis species A, B P. triplehorni sp. nov., holotype (male, prior to dissection), habitus A dorsal B ventral B, C P. praeclarus (male, from Piracicaba, Sao Paulo) B dorsal C ventral E, F P. wittmeri holotype (male), habitus E dorsal F ventral. Scale bars: 1 mm (A-D).

Figure 2. Petalacmis triplehorni sp. nov., male head A-F core head A dorsal B ventral / occipital C frontal D lateral E posterior H, I antenna H lateral I frontal. Scale bars: 250 µm (A-E); 500 µm (H, I).

Figure 3. Petalacmis triplehorni sp. nov., male thorax. A-E prothorax: A dorsal B ventral C anterior D posterior E lateral. F-K pterothorax: F mesoscutellum, dorsal G alinotum, dorsal H pterothorax, ventral I pterothorax, dorsal (detail of meso and metaendosterna J alinotum, dorsal K pterothorax and abdominal tergum I, lateral L-N wings: L elytron, dorsal M elytron, lateral (outer view) N left wing, dorsal O, P legs: O left pro, meso and metaleg (left to right) P detail of left pro, meso and metaleg apices (left to right). Scale bars: 500 µm (A-K); 1 mm L-N; 750 µm (O); 250 µm (P).

Figure 4. Petalacmis triplehorni sp. nov., male abdomen A-C core abdomen (segments IV-VIII) A dorsal B lateral C ventral D-F aedeagal sheath D dorsal E lateral F ventral G-J aedeagus (distal tips oriented toward top of the figure) G apical / posterior H dorsal I lateral, J ventral. Scale bars: 500 µm (A-C); 250 µm (D-I).