A revision of Peltariosilis Wittmer (Coleoptera: Cantharidae), a surprisingly diverse Amazonian radiation

Peltariosilis Wittmer, 1952 is a South American Silinae genus characterised by the highly modified male pronotum and scutellum with a remarkable lamellar projection. Six species were previously recognised. The study of numerous specimens from previously unsampled localities and the revision of previously studied material shows that Peltariosilis is far more diverse than previously recognised. 15 species are here recognised as valid, nine of which are described as new: P. brancuccii, P. brunneoapicalis, P. cleidecostae, P. diversicollis, P. flavicornis, P. gracilicornis, P. major, P. orientalis and P. parviscutellaris spp. nov. A comparative study and new morphological terminologies are introduced for pronotum, scutellum and male genitalia. All Peltariosilis species are described and illustrated, including the first illustration of a female pronotum, and an identification key is provided. A map is given, including records of all known Peltariosilis, showing a distribution confined to the Amazonian subregion (Suriname, French Guiana, N Brazil, E Peru and NE Bolivia). The identity of the type species P. scutulata (Wittmer, 1952), hitherto considered as broadly distributed and highly variable, is addressed through study of their type series and additional specimens from widespread localities.


INTRODUCTION
Silinae are the second largest subfamily of Cantharidae in terms of described species. They are found on all continents but particularly diverse in the tropics. One of the most remarkable features of this subfamily is the high diversity of complex sexually dimorphic structures found in the males, all presumed to be associated with pheromone glands and used during mating (Eberhard, 2006;Hsiao et al., 2015). In most Silinae genera, these male "modifications" are located on the pronotum and are highly diagnostic species characters. One of the most remarkable examples is Peltariosilis Wittmer, 1952 from the Amazonian region of South America, where not only the male pronotum is highly complex, but also the scutellum bears a remarkable modified projection, in the shape of an obliquely or perpendicularly rising lamella, sometimes with a forked apex. This kind of structure is unique within Cantharidae.
Using a very wide concept of the genus Silis Charpentier, 1825, Wittmer (1952) established the subgenus Peltariosilis for two species, Silis scutulata Wittmer, 1952from Manaus, Brazil, and S. guyanensis Pic, 1906from French Guiana. Later, Wittmer (1966 described P. amapaensis from Amapá state, northern Brazil. Constantin (2010a) assessed the morphology of the three known species and elevated Peltariosilis to genus rank, adding as diagnostic characters the long, stout mandibles with a tooth at their base, the very short and widely emarginated epistoma, the very thin, short and adpressed elytral pubescence, the pronotum with anterior and posterior projections, and characters of the aedeagus. Also, he provided an identification key and new distributional records for the species.
As a result of long-term prospections in French Guiana, Constantin (2017) revised Peltariosilis and doubled the number of known species describing P. mensaemontis, P. mitarakaemontis and P. lamellata, and presented reliable illustrations of diagnostic features and a new identification key. Also, the distribution of species was expanded, especially for P. scutulata, broadly recorded throughout the Amazonian part of Brazil (Amazonas, Pará and Acre states), Peru and Bolivia (Constantin, 2017;Constantin & Chaboo, 2016). ISSN On-Line: 1807-0205 ISSN Printed: 0031-1049 ISNI: 0000-0004-  Label data are given verbatim. Information for each specimen is within quotation marks, labels are separated by double slashes (//), and single slashes (/) separate lines on the same label. All specimens of new species bear our red holotype or paratype label with taxon name. Complementary information is given within square brackets.
General morphological terminology used in the descriptions and dissection methods follow Brancucci (1980) and Constantin (2015). A new terminology is proposed for pronotal and scutellar structures. Until today, there is no universally accepted terminology for aedeagus structures within the subfamily Silinae. Therefore, the terminology from Constantin (2015) is used here to facilitate the comparison with other Neotropical genera of Silinae (e.g., Constantin, 2015Constantin, , 2017Biffi & Constantin, 2018).
Photographs were taken on a Zeiss AxioCam MRc 5 video camera attached to a Carl Zeiss Discovery stereomicroscope or with Canon EOS Rebel T3i camera with Canon MP-E 65 mm macro-lens and StackShot macro-rail. Multi-focus images were combined with Zerene Stacker version 1.04. Illustrations were produced via camera lucida attached to stereomicroscope. Illustrations and photographs were edited in Adobe Photoshop CS6 and Adobe Illustrator CS6. The species are organised in the text and plates by similarity in order to enable an easier morphological comparison. For species that were recently described and well-illustrated (see Constantin, 2017) we provide only a differential diagnosis.
The general distribution map was created with Quantum GIS version 2.18.7-1 (available at http://www. qgis.org). Localities in the map are approximate localities obtained from specimens' labels and published literature sources (Constantin, 2010a(Constantin, , 2017. lucent. Body regularly covered with dense very short and fine adpressed pubescence and sparse longer setae on antennae and abdomen. Males: Head (Fig. 1A) (including eyes) broad, nearly as wide as pronotum, ventral part retracted; gula long, gular sutures broadly separated; occipital region and vertex broadly convex, frons flattened; clypeus broadly fused to frons, frontoclypeal suture absent; clypeus broad, slightly prominent, anterior margin with an arched notch; labrum membranous, very reduced, barely distinct in frontal view; genae very short, indistinct in front of eyes. Eyes prominent, bulging, rounded, nearly as long as wide, broadly separated. Antennal insertions broadly separated; antennae usually filiform, sometimes with swollen, rounded antennomeres. Mandibles (Fig. 1A) long, stout, apex acute and sharp, smooth or with a minute tooth near base, lateral margins with rather long and dense pubescence. Maxillae weakly sclerotised; stipes short and broad, galea and lacinia membranous, densely setose; maxillary palpi longer than stipes; palpomeres I-III similar in shape, elongate, IV securiform. Labium weakly sclerotised, submentum membranous, palpi 3-segmented, palpomere III securiform. Pronotum (Figs. 2, 10) variously modified; anterior margin broadly arched, sides forming a frontolateral lobe (fl); sides behind frontolateral lobe parallel to slightly convergent posteriorly, distalmost part forming a broad or narrow laterobasal lobe (lbl) directed up and medially; angles (ang) of laterobasal lobes acute, obtuse, rounded or forming an unciform spine; apex of laterobasal lobe entire or divided into dorsal (df ) and ventral flaps (vf ). Dorsal surface forming two lateral bumps divided by a median groove (mg), a pair of dorsal projections (dp) that may be broadly rounded or sharp, razor blade shape, sometimes merging with laterobasal lobe; a deep basal groove (bg) behind laterobasal lobes; a pair of glandular pores anteriorly (gp). Scutellum (Figs. 2,12) projected (sp) upwards and anteriorly in a broad trapezoidal lamella (Figs. 2C, 12A-F) or in a narrow stem divided apically in a bifid, well-defined fork (Figs. 2F,. Elytra smooth, long, completely concealing the wings and abdomen; lateral sides parallel to divergent, wider posteriorly; apex rounded to nearly truncate; lateral and sutural margins not forming distinct borders. Thorax weakly sclerotised, metaventrite convex. Legs small, slender, without strong modifications in size, shape or pubescence; tibiae with one pair of tiny apical spurs; fourth tarsomere with a transversal slit at base; anterior fore tarsal claws with a small rounded basal lobe; anterior mid hind tarsal claws with a small straight basal cleft. Wings (Fig. 3) short and broad, radial cell 2R₁ closed, veins r and r-m not coinciding in the meeting point of Rr, Rr prolonged anteriorly beyond the meeting point of r-m, vein cu-a weakly sclerotised, barely visible, anal vein (A) not divided. Abdomen weakly sclerotised, flattened, short and broad; glandular pores very small, barely visible, not prominent, located near the distal margin of tergites; tergite VIII ( Fig. 13) long and broad, with lateral margins straight to arched, glandular pores shallow to rather prominent, distal margin variously notched; ventrites I-VI very wide, distal margin straight; ventrite (i.e., visible sternite) VII (Fig. 14) with a very deep longitudinal incision, dividing it into two halves. Aedeagus (Figs. 4,(15)(16)(17): ventral plaque of tegmen (tg) lateral, flattened, very elongate, nearly as long as internal sac, variously shaped, straight, curved or sinuous, apex acute, rounded or truncate; parameres (p) dorsally, united at base and moderately to broadly divergent from mid length, elongate, broadly curved dorsally, apex acute; median lobe (ml) thinly membranous, translucent, tubular around internal sac and a series of sclerites; internal sac (is) membranous, very elongate, slender, straight to slightly curved dorsally, apex sometimes slightly swollen; a series of sclerites variable in number, position and shape: one pair of median dorsal sclerite (mds) that can be separated, fused medially or totally fused forming one single median sclerite, dorsal, very elongated, straight to curved ventrally, apex acute; one pair of paramedian dorsal sclerites (pds) robust, strongly sclerotised, flattened, usually curved or inclined dorsally, apex acute, gradually or abruptly narrowed, sometimes with scratches or projecting teeth; one pair of ventral sclerites (vs) very long, slender, pressed against ventrolateral wall of internal sac, apex acute, usually directed laterally; one pair of lateral sclerites (ls) present or absent.
Female: Similar to males in colouration and general morphology, differing from males on the base of dimorphic features, such as the antennae not swollen at middle antennomeres, pronotum (Fig. 11) wider and flattened, without strong modifications, anterior margin less arched, frontolateral and laterobasal lobes rounded, short, not pronounced or recurved; scutellum flattened, not projected anteriorly; pygidium more transverse; abdominal ventrite VII entire, not longitudinally divided, not distinctive among species.
Apex of laterobasal lobe of pronotum broad, truncate, directed posteriorly (Fig. 10C)     lateral unciform spine, posterior portion with an acute pointing projection posteriorly; prediscal projections convex, broadly rounded, not meeting dorsal edge of laterobasal lobe. Scutellar projection short, trapezoidal, lamellar, slightly narrowed at apex, distal margin sinuated, with three shallow rounded projections. Peltariosilis amapaensis is similar to P. lamellata, P. guyanensis, P. mensaemontis and P. diversicollis sp. nov. by the general aspect of pronotum. It differs from these species by the posterior margin of dorsal projections of pronotum with an acute pointing tip.

Re-description:
Head entirely black; maxillae and labium light brown, slightly darker on distal palpomeres; antennae mostly dark brown, slightly lighter at base of each antennomere, antennomeres I-II orangish to light brown; pronotum and scutellum light orange brown, slightly translucent; elytra dark brown, lighter at lateral margins; legs light orange brown, darker on the apex of tibiae and tarsi; thorax and abdomen dark brown, darker on last abdominal ventrite and tergite.
Female: General appearance and colouration similar to males; antennae slender, simple, middle antennom-eres not distinctly globose; pronotum (Fig. 11A) without strong modifications; frontolateral lobe smaller, posterior margin arched; laterobasal lobe broad, oblique; dorsal projections absent; median and basal grooves shallow; ventrite VII with a small median notch on distal margin.
Remarks: Pic (1906) described this species from an unspecified number of males from "Cayenne". We found three male specimens at MNHN and NHMB, all with different locality data, which we here consider part of the original type series. This includes a specimen at NHMB cited as a non-type by Constantin (2010a), which however bears a "cotype" label in Pic's handwriting. The male syntype at MNHN, in Pic's own collection, is here designated as the lectotype. Diagnosis: Head and antennae black, except for antennomere I and ventral face of II, pronotum orangish, scutellum reddish, legs orangish yellow, distal half of tibiae and four basal tarsomeres infuscate. Male (Fig. 5D): Antennae long, antennomeres V-VIII swollen, ovoid, IX-XI slender, narrower than preceding ones. Pronotum (Fig. 10D): anterior margin arched, broadly continuous with frontolateral lobes; sides behind frontolateral lobe concave; laterobasal lobe not projected laterally, curved posteriorly; angles of laterobasal lobe forming long, acute spikes; dorsal projections broad, distal margin rounded, directed dorsally. Scutellum (Fig. 12D) with vertical trapezoidal lamellar projection, as long as wide at base, apex truncate. Peltariosilis lamellata differ from P. amapaensis by the angles of laterobasal lobes of pronotum forming long, slightly curved spikes, and dorsal projection shorter, posterior margin rounded, directed dorsally.

Peltariosilis mensaemontis
Distribution: French Guiana (Fig. 18). Diagnosis: Pronotum with laterobasal lobe flattened, slit posteriorly into dorsal and posterior flaps with acute pointing projections posteriorly, and lateral unciform spine; dorsal projections flattened, broadly rounded, meeting dorsal edge of laterobasal lobe; sides of laterobasal lobes visible laterally, not concealed under dorsal projections. Scutellum with a short trapezoidal lamellar projection, wider than long, wide at base. Peltariosilis diversicollis sp. nov. differs from P. lamellata by the curved, unciform spines at the angles of laterobasal lobes, from P. major sp. nov. by the broad dorsal projections of pronotum, and from P. amapaensis, P. guyanensis and P. mensaemontis by the lateral sides of laterobasal lobes not concealed under dorsal projections.

Peltariosilis diversicollis
Description: Head entirely black; maxillae and labium light orange brown, slightly darker on distal palpomeres; antennae mostly dark brown, slightly lighter at dorsal surface of antennomeres IV-VIII; antennomeres I-II and apex of XI orangish to light brown; pronotum and scutellum light orange brown, slightly translucent; elytra dark brown, lighter at lateral margins; legs light orange brown, darker on the apex of tibiae and tarsi; thorax and abdomen dark brown, darker on last abdominal ventrite and tergite.

Female: Unknown.
Etymology: The epithet diversicollis is formed from the Latin words diversus (different) + collum ("neck", prothorax), referring to the distinct shape of prothorax in this species.
Distribution: Brazil (Amapá state) (Fig. 18).  Description: Head mostly black, slightly lighter at anterior margin of clypeus; maxillae and labium testaceous yellow; mandibles light brown, darker apically; antennae mostly black, antennomeres I-II orange brown, X-XI dark brown; pronotum and scutellum light orange brown, slightly translucent; elytra dark brown, lighter at lateral margins; legs light orange brown; thorax and abdomen dark brown.

Female: Unknown.
Etymology: The specific epithet major (Latin for "larger") refers to the larger size of the species in comparison with the others.

Peltariosilis gracilicornis
Description: Head black, except anterior margin of clypeus, orange brown; mandibles, labium, maxillae and palpi testaceous to light brown; antennae entirely testaceous yellow; pronotum and scutellum orange brown, slightly translucent; elytra dark brown, lighter at lateral margins and along suture; legs testaceous yellow to light orange brown slightly darker at apex of tibiae and tarsi; thorax and abdomen dark brown, except near the distal and lateral margins of abdominal ventrites.
Distribution: Brazil (Amazonas state) (Fig. 18). ( lighter at lateral margins and along suture. Antennomeres X-XI narrower than preceding ones. Pronotum with low, sharp dorsal projections; laterobasal lobes straight, di-rected dorsally and posteriorly, apex rounded, swollen. Scutellum with a long forked projection; apices parallel, pointing anteriorly. Peltariosilis scutulata is a member of a group of species with somewhat similar pronotum and scutellar projections. It differs from P. mitarakaemontis, P. brunneoapicalis sp. nov. and P. parviscutellaris sp. nov. by the robust apices of scutellar fork, from P. cleidecostae sp. nov. and P. brancuccii sp. nov. by the rounded apex of laterobasal lobes; from P. gracilicornis sp. nov. and P. flavicornis sp. nov. by the mostly dark brown antennae, and from P. orientalis sp. nov. by the width of dorsal projections of pronotum, reaching lateral margins.

Re-description:
Head black, except anterior margin of clypeus, orange brown; mandibles, labium, maxillae and palpi testaceous to light brown; antennae mostly dark brown, except antennomeres I-II, ventral face of III, and X-XI testaceous yellow to light orange brown; pronotum and scutellum orange brown, slightly translucent; elytra dark brown, lighter at lateral margins and along suture; legs testaceous yellow to light orange brown slightly darker at apex of tibiae and tarsi; thorax and abdomen dark brown, except near the distal and lateral margins of abdominal ventrites.
[Benjamin] Constant" (Fig. 9J). The reason why the type specimens of S. scutulata are labelled as "paratype" and "allotype" is still unknown, but one of them actualy might comprise the holotype. The specimen labelled as "allotype" is here considered as the actual holotype of S. (P.) scutulata, given that that is the only specimen bearing a label with the type locality according to the original description. Fortunately, since the original description, this specimen had never been returned to the MNRJ, thus being saved from the fire that destroyed nearly the entire museum in September, 2018 (Kury et al., 2018).
On the identity of P. scutulata: In the two most recent papers on the genus (Constantin & Chaboo, 2016;Constantin, 2017), this species was reported to be widely distributed within the Amazonian forests, from French Guiana and Pará state (Brazil) to Bolivia and Peru. With the limited amount of material available per locality, the diagnosis of the species was based only on external characters. Now, our more extensive material and the examination of the male genitalia revealed clear differences between the populations in various parts of Amazonia, which lead us to the conclusion that P. scutulata sensu Constantin needs to be treated as a whole complex of species. What added to the confusion was the fact that Wittmer's own type series already represents two different species, with the paratype from Benjamin Constant belonging to a different, undetermined species. The remaining specimens identified as P. scutulata by Wittmer himself turned out to belong to three additional species (P. cleidecostae sp. nov., P. flavicornis sp. nov. and P. brancuccii sp. nov.). It appears that both Wittmer and Constantin interpreted the differences in pronotum structure, scutellar projection and antennal colouration as individual variability, but with our more extensive material some of these character turned out to be diagnostic for the different species.
With this in mind, we have to assume that the specimen illustrated by Constantin (2017) most likely doesn't belong to P. scutulata either, but at the moment we are not sure which species to assign it to. In our restricted sense, P. scutulata is a species found only in parts of Amazonian Brazil, notably around Manaus. Some records from other areas mentioned by Constantin (2017) are still pending re-examination. / 13.XI.1966" (2 ♂, NHMB, 1 ♂, BMNH); "BRASIL. MT, Nova Mutum / Fazenda Buriti / 04 -14.i.2002 -Luz / HF Mendes Col." (2* MZUSP 31242-31243).
Diagnosis: Antennae entirely pale yellow; pronotum and scutellum orange yellow; elytra dark brown, slightly lighter at lateral margins. Antennomeres X-XI slightly narrower than preceding ones, middle antennomeres not distinctly swollen. Pronotum with low, sharp dorsal projections; laterobasal lobes curved, directed dorsally and posteriorly, apex rounded, divided in two flaps. Scutellum with a long, forked projection; apices acute, divergent, pointing latero-anteriorly. Peltariosilis flavicornis sp. nov. is similar to P. gracilicornis sp. nov. by the entirely pale yellow antennae. They differ by the scutellar projection much narrower at middle in P. flavicornis sp. nov.
Description: Head black, except anterior margin of clypeus, dark brown; antennae, labium, maxillae, palpi and base of mandibles pale yellow, apex of mandibles light brown; pronotum and scutellum orange brown, slightly translucent; elytra dark brown, lighter at lateral margins; legs entirely testaceous yellow to light orange yellow; thorax and abdomen dark brown.
Female: General appearance and colouration similar to males, antennae thinner and shorter than in male, middle segments not thickened. Eyes smaller and less protruding. Pronotum as in (Fig. 11B).

Etymology:
The specific epithet flavicornis is formed from the Latin words flavus (yellow) + cornis ("horn", antenna), referring to the yellow antennae.

Diagnosis:
Antennae not distinctly swollen, ventral surface slightly flattened, antennomeres I to basal half of III testaceous yellow, the following dark brown, X-XI orange yellow; pronotum and scutellum orange brown; elytra dark brown, testaceous yellow at lateral margins and along sutures; pronotum with low, dull dorsal projections, not reaching lateral margins of pronotum; wellmarked angles at laterobasal lobe; laterobasal lobes curved, apex rounded, divided in two flaps; scutellum with a long forked projection; apices short, acute, divergent, pointing latero-anteriorly. Peltariosilis orientalis sp. nov. is similar to P. scutulata by the general body colouration and shape of scutellar projection. Peltariosilis orientalis sp. nov. differs by the less prominent anterior margin of pronotum, continuous with frontolateral lobes, which are broader; dorsal projection of pronotum shallower, and shorter laterally; apices of scutellar projection shorter.
Description: Head black, except anterior margin of clypeus, dark brown; labium, maxillae, palpi and base of mandibles orange yellow, apex of mandibles dark brown; antennomeres I to basal half of III testaceous yellow, the following dark brown, X-XI orange yellow; pronotum and scutellum orange brown, slightly translucent; elytra dark brown, testaceous yellow at lateral margins and along sutures; legs orange yellow, slightly infuscate at distal tarsomeres; thorax and abdomen dark brown.
Male: (Fig. 6D): Antennae rather short; antennomere I elongate, slightly wider apically, II short, slightly wider apically, III-IX nearly oblong, narrower proximally, flattened at ventral surface, X-XI slightly narrower, slender. Anterior margin of clypeus with a broad arcuate concave notch. Pronotum (Fig. 10J): anterior margin broadly arched, continuous with frontolateral lobes; frontolateral lobe broad, sides rounded, sides behind frontolateral lobe rounded, slightly convergent; angles of laterobasal lobe obtuse, well-marked; laterobasal lobe directed posteriorly and dorsally, posterior margin straight, anterior margin sinuous, apex swollen, rounded, split, forming juxtaposed dorsal and ventral flaps; apex of ventral flap with a short membranous projection; dorsal projections low, transverse, directed postero-dorsally, distal margin slightly arcuate, forming an inner dull peak and short lateral peaks not reaching sides of pronotum. Scutellum (Fig. 12J) with a long forked projection anteriorly; scutellar projection strongly narrowed at middle and gradually widened and split towards apex, forming apical fork with arched sides; apices of fork short, divergent, pointing anteriorly. Elytra nearly parallel, apex rounded. Abdominal tergite VIII (Fig. 13G) subtrapezoidal, lateral margins broadly arched, wider anteriorly, slightly convergent posteriorly, glandular pores strongly protruding, distal margin with a broad and deep concave median notch. Ventrite VII (Fig. 14G) wide, trapezoidal, lateral margins wider anteriorly, convergent posteriorly; posterior margins straight laterally, with a low rounded projection internally. Aedeagus ( Fig. 16M-P): ventral plaque of tegmen lateroventral, elongated, as long as internal sac, flattened laterally, curved internally, lateral margins arched, broad at base, narrowed at middle, wider at apex, apex broadly rounded with a dorsally curved acute tip; parameres fused at base and slightly divergent, regularly curved dorsally, apex narrowed with a small acute tip; median lobe membranous, translucent; internal sac elongated, narrow, straight, slightly sclerotised; one single median dorsal sclerite, elongated, narrow, apex acute; paramedian dorsal sclerites robust, strongly sclerotised, elongated, parallel, slightly curved dorsally, apex narrowed and divergent, pointing laterally; ventral sclerites slender, as long as internal sac, apex acute, slightly divergent; lateral sclerites indistinct or absent. testaceous yellow, III-IX gradually infuscate; pronotum and scutellum testaceous yellow, slightly translucent; elytra dark brown, slightly lighter at lateral margins; pronotum with low, sharp dorsal projections, lateral peaks short, not reaching lateral margins of pronotum; apex of laterobasal lobes truncate, oblique, divided in two flaps; scutellum with a long forked projection strongly narrowed at middle and abruptly widened and split towards apex, forming apical fork, apices of fork acute, long, parallel, pointing anteriorly. Peltariosilis cleidecostae sp. nov. is very similar to P. brancuccii sp. nov. Both distinguish from other species by the shape of scutellar projection strongly narrowed at middle then abruptly widened, with parallel apices, and by the truncate and oblique apex of laterobasal lobes. Peltariosilis cleidecostae sp. nov. is distinguished by the more projected anterior margin of pronotum, dorsal projections wider, almost reaching lateral margins of pronotum, and shorter scutellar projection.
Description: Head black, except anterior margin of clypeus, light brown; labium, maxillae, palpi and base of mandibles pale yellow, apex of mandibles light brown; antennomeres I-II and X-XI testaceous yellow, III-IX gradually infuscate, dark brown; pronotum and scutellum testaceous yellow, slightly translucent; elytra dark brown, slightly lighter at lateral margins; legs testaceous yellow, slightly infuscate at tarsi; thorax and abdomen dark brown.
Male: (Fig. 6E): Antennae rather long; antennomere I elongate, slightly wider apically, II short, cylindrical, III-IX nearly oblong, narrower proximally, flattened at ventral surface, X-XI slightly narrower, slender. Anterior margin of clypeus with a broad arcuate concave notch. Pronotum (Fig. 10K): anterior margin arched, projected; frontolateral lobe narrow, not continuous with anterior margin, sides rounded; angles of laterobasal lobe indistinct, broadly rounded; laterobasal lobe directed posteriorly and dorsally, posterior margin rounded, apex truncate, oblique, split, forming juxtaposed dorsal and ventral flaps; apex of ventral flap with a broad membranous projection; dorsal projections low, transverse, directed postero-dorsally, distal margin arcuate, sharp, forming an inner acute peak and short lateral peaks not reaching sides of pronotum. Scutellum (Fig. 12K) with a long forked projection anteriorly; scutellar projection strongly narrowed at middle and abruptly widened and split towards apex, forming apical fork with arched sides; apices of fork acute, long, parallel, pointing anteriorly. Elytra nearly parallel, apex rounded. Abdominal tergite VIII (Fig. 13H) nearly as long as wide, lateral margins broadly arched, wider medially, glandular pores not protruding, distal margin with a broad and deep concave median notch. Ventrite VII (Fig. 14H) wide, lateral margins arched, wider medially; posterior margins with broad rounded projections near middle. Aedeagus (Fig. 17A-D): ventral plaque of tegmen laterally, elongated, nearly as long as internal sac, flattened laterally, nearly straight, broader at base, gradually narrowing at apex and slightly curved internally, with a dorsally curved acute tip; parameres fused at base and slightly divergent, slightly curved dorsally, apex narrowed, strongly curved dorsally, with acute tip; median lobe membranous, translucent; internal sac elongated, narrow, straight; one single median dorsal sclerite, elongated, narrow, apex acute, arched at base, straight from middle; paramedian dorsal sclerites robust, strongly sclerotised, elongated, apex strongly curved dorsally, before the apex with a number of irregular furrows; ventral sclerites slender, shorter than internal sac, apex acute, slightly divergent; lateral sclerites indistinct or absent.

Diagnosis:
Antennae not distinctly swollen, ventral surface slightly flattened, antennomeres I-II light brown, III-IX dark brown to black, X-XI orange brown; pronotum and scutellum orange brown to light brown, slightly translucent; elytra dark brown to black, slightly lighter at lateral margins; pronotum with low, sharp dorsal projections, lateral peaks very short, not reaching lateral margins of pronotum; apex of laterobasal lobes truncate, oblique, divided in two flaps; scutellum with a long forked projection strongly narrowed at middle and abruptly widened and split towards apex, forming apical fork, apices of fork acute, long, parallel, pointing anteriorly. Peltariosilis brancuccii sp. nov. is very similar to P. cleidecostae sp. nov. It distinguishes from the later by the less projected anterior margin of pronotum, contiguous with frontolateral lobes, dorsal projections narrower, and longer scutellar projection.

Female: Unknown.
Etymology: The specific epithet is patronymic, named in honour of the second author's late advisor, Dr Michel Brancucci (1950Brancucci ( -2012, in appreciation of his contributions to Cantharidae systematics and in gratitude for his constant encouragement to specialise in the neglected "malacoderm" families Cantharidae and Prionoceridae. Distribution: Bolivia and Brazil (Acre state) (Fig. 18).  (Wittmer, 1966). (B) P. guyanensis (Pic, 1906). (C) P. mensaemontis Constantin, 2017  IV-VIII light to dark brown; thorax and abdomen light to dark brown; pronotum and scutellum orange yellow, slightly translucent; legs and elytra testaceous yellow, except for broad, irregular light to dark brown apical elytral patches.

Female: Unknown.
Etymology: The specific epithet brunneoapicalis is formed from the Latin words brunneus (brown) + apicalis (apical), referring to the elytral apical brown spots.

Distribution and natural history of Peltariosilis
With the new species described herein, the number of known Peltariosilis species is more than doubled. In addition to the 15 species now recognised, we have currently unidentified material from some more localities (see Fig. 18) currently pending further studies, so we can expect the number of species to rise even further as more material becomes available. All of the species are restricted to the Amazonian subregion of the Neotropical region (sensu Morrone, 2000), with only P. flavicornis extending into the southern fringes of that area in Mato Grosso state, Brazil.
Based on the limited biological data available to us, mostly just the labels of the specimens, we can extrapolate that Peltariosilis are generally associated with forests, and most often with humid evergreen forests. One species, P. orientalis from Maranhão, was collected in an ecotone area between Amazon forest, savannah and Atlantic rainforest, with the exact habitat being unknown. Peltariosilis lamellata was collected at a light trap placed in a rocky savannah on top of a table mountain. Peltariosilis scutulata and P. cleidecostae are recorded from flooded forests (igarapés) in Acre and Roraima states. Most species were collected at rather low elevations, with only P. mensaemontis reaching 800 m on one of the "inselbergs" in French Guiana.
An interesting result of our study is the high morphological similarity between some of our species (e.g., P. cleidecostae sp. nov. and P. brancuccii sp. nov.), which makes them hard to separate based on external characters and has already led to some confusion regarding Wittmer's definition of P. scutulata. Despite the highly complex and diverse pronotum and scutellum characters in the male, it is recommended to always examine the aedeagus for reliable identification, with the females being only identifiable when unambiguously associated with a male at the same locality. All this indicates that Peltariosilis have radiated within the Amazonian subregion rather recently. The once widespread hypothesis of allopatric speciation in Amazonian taxa due to Pleistocene forest fragmentation (e.g., Vanzolini & Williams, 1970) is now increasingly being challenged (e.g., Knapp & Mallet, 2003;Bush & Oliveira, 2006). As long as the real biogeographic history of the Amazon forests is very much disputed (Hooghiemstra, 2001), we would like to refrain from making any guesses on when Peltariosilis could have radiated. The complex structures of pronotum and scutellum in male Peltariosilis, likely associated with sexual pheromones (Eberhard, 2006), may have been driving speciation by increasing the reproductive isolation between populations.
It is evident that some Peltariosilis species have a rather restricted distribution within the Amazonian subregion. A number of species (P. gracilicornis, P. lamellata, P. major, P. mensaemontis, P. mitarakaemontis, P. orientalis) are only known from a single locality. The species known from multiple localities are confined to either South or North of the Amazon main course, with several species (P. amapaensis, P. diversicollis, P. guyanensis, P. lamellata, P. major, P. mensaemontis, P. mitarakaemontis) restricted to the Guianas including Amapá ("Moist Guianian province" of Morrone, 2000). Figure 18. Distribution of Peltariosilis species. Biffi, G. & Geiser, M.: Revision of Peltariosilis Wittmer Pap. Avulsos Zool., 2020;v.60.special-issue: e202060(s.i.).16 25/26 The vast majority of the specimens examined herein came from light traps. Two species (P. major and P. scutulata) were reportedly beaten from vegetation during the day. Peltariosilis amapaensis was collected in flight intercept traps and P. mitarakaemontis was present in SLAM (sea-land-aerial-Malaise trap), as well as light trap samples (Constantin, 2017). Based on this, we can assume that Peltariosilis are predominantly nocturnal. The collecting dates of most type series indicate that many species may also be highly seasonal, with a short adult lifespan, although further material is needed to confirm this assumption.