Systematics of the Ceracis furcifer Species-Group (Coleoptera: Ciidae): The Specialized Consumers of the Blood-Red Bracket Fungus Pycnoporus sanguineus

The Ceracis furcifer species-group (Coleoptera: Ciidae) originally comprised nine species names: Ceracis cornifer (Mellié, 1849); C. cylindricus (Brèthes, 1922); C. furcifer Mellié, 1849; C. hastifer (Mellié, 1849); C. monocerus Lawrence, 1967; C. ruficornis Pic, 1916; C. simplicicornis (Pic, 1916); C. semipallidus Pic, 1922 and C. unicornis Gorham, 1898. Ceracis semipallidus was synonymised with C. furcifer and then no further changes were made to the composition of the group. Here, we provide a taxonomic revision of the Ceracis furcifer species-group and new data on the geographic distribution and host fungi of the included species. Lectotypes are designated for C. cornifer, C. furcifer, C. hastifer, C. ruficornis, C. semipallidus and C. unicornis. As results we: (i) synonymise C. cylindricus, C. monocerus, C. simplicicornis, C. unicornis with C. cornifer; (ii) confirm the synonymy of C. semipallidus with C. furcifer; (iii) redescribe C. cornifer, C. hastifer, C. furcifer and C. ruficornis; and (iv) provide an identification key for species in the furcifer group. The frontoclypeal horn and body coloration showed great intraspecific variation. We show that species in the furcifer group have distributions wider than previously known and use mainly Pycnoporus sanguineus as host fungus. Species of the furcifer group are the only animals specialized in feeding on basidiomes of P. sanguineus.

The Ceracis furcifer species-group (Coleoptera: Ciidae), as proposed by Lawrence [3], includes nine species names: Ceracis cornifer (Mellié, 1849); C. cylindricus (Brèthes, 1922); C. furcifer Mellié, 1849; C. hastifer (Mellié, 1849); C. monocerus ; C. ruficornis ; C. simplicicornis ; C. unicornis Gorham, 1898 and C. semipallidus Pic, 1922. Hereafter, the Ceracis furcifer species-group will simply be called the "furcifer group". When the furcifer group was defined, in the same paper Lawrence Terms for external morphology and male abdominal terminalia of ciids used here largely follow Lopes-Andrade and Lawrence [36]. We do not include a study of the female abdominal terminalia, due to technical difficulties (e.g., small size and membranous parts) and the absence of morphological features to clearly distinguish females. Therefore, females were not included in the identification key. Range, mean and standard deviation values for measurements (in millimeters) and ratios are provided in redescriptions and the following abbreviations are used: BW, basal width of the scutellum; CL, length of the antennal club (measured from base of the first antennomere of the club to apex of the last); EL, elytral length (at midline, from base of scutellum to elytral apex); EW, greatest elytral width; FL, length of the antennal funicle (measured from base of the third to apex of the last antennomere before the club); GD, greatest depth of the body (from elytra to metaventrite); GW, greatest diameter of the eye (measured laterally); HL, length of male frontoclypeal horn in lateral view, slightly below baseline of horn (because this is generally concave) to the apex; PL, pronotal length along midline; PW, greatest pronotal width; and TL, total length (=EL + PL; head not included). The ratio GD/EW was recorded as an indication of degree of convexity; TL/EW indicates degree of body elongation. A maximum of five males and five females from each locality were measured but, in some cases, individuals from close localities were not measured. Differences between specimens are given in the sections on variation, together with standard measurements and ratios.
Pin label transcriptions are placed within quotation marks, with each label separated by a backslash. Unless otherwise specified (between square brackets), labels are printed on white paper. The number of individuals bearing these labels is stated immediately before label data. The following federal states of Brazil  Individuals were examined, compared, measured and photographed under a Zeiss Discovery V20 equipped with a Zeiss AxioCam 506 digital camera. Whole mount preparations of male abdominal terminalia followed the protocol described by Lopes-Andrade [37] and photography of dissected pieces was performed under a Zeiss AxioLab compound microscope equipped with a Zeiss AxioCam MRc digital camera. Distribution maps were created in the freeware QGIS 2.12.2 [38], with latitude and longitude coordinates estimated by tracking localities in the online database GeoNames [39]. Maps include all localities of individuals directly examined by us and all previously published records. Maps based on annual temperature means were based on the Bioclim dataset, obtained from a global climate database with high spatial resolution (free climate data for ecological modelling and GIS, version 1.4; www.worldclim.org [40]).
The term "breeding record" considered here follows the definition proposed by previous authors [21,22]. "A ciid species was recorded as breeding in a fungus if at least one of the following criteria was met: the presence in a fungus collection of (1) at least 10 fully pigmented adults; (2) two or more tenerals; or (3) one teneral and two or more mature (fully pigmented) adults" [22]. The term "Tenerals" refers to adults recently eclosed and light-coloured [22]. Breeding records provide robust evidences that the presence of a ciid species in a fungus is not incidental.

Results
For nomenclatural stability, lectotypes are designated for C. cornifer, C. furcifer, C. hastifer, C. ruficornis, C. semipallidus and C. unicornis. The lectotype of C. ruficornis was designated based on annotations made by Dr. John F. Lawrence, a ciid specialist who directly examined the type series in 1965, and photos by Dr. Vivian. E. Sandoval-Gómez, who photographed the lectotype and labels in 2011 and made available the photos to us. Based on patterns of external morphology of adults, including male abdominal terminalia, we propose to (i) synonymize C. cylindricus, C. monocerus, C. simplicicornis and C. unicornis with C. cornifer; (ii) confirm the synonym of C. semipallidus with C. furcifer previously proposed by Lawrence [3]; (iii) provide redescriptions for C. cornifer, C. hastifer, C. furcifer and C. ruficornis, here considered valid species of the furcifer group; (iv) provide an identification key for furcifer group species. Evidence and arguments for the taxonomic acts proposed here are provided in the Species Accounts, especially with respect to the new synonyms of C. cornifer (see "Remarks").
The records of animals feeding on basidiomes of P. sanguineus are compiled in Table A1, together with breeding records when available. Table A2 provides information on all other host fungi used by furcifer group.         arrow); prosternal process thin but not laminate (white arrow), (B) pronotal punctation, (C) first abdominal ventrite with a sex patch at the centre (white arrow), (D) male terminalia, showing sternite VIII (with a deep concave emargination at middle, black arrow), tegmen (teg), penis (pen, basal edge blunts; black arrows), (E) labels of the lectotype deposited in the Muséum National d'Histoire Naturelle, MNHN (Paris, France), (F) female plesiotype from Viçosa (MG, Brazil). Scale bars: A = 0.5 mm, B = 0.2 mm, C,D = 0.1 mm, F = 0.5 mm.    Diagnosis. Each lateral contour of male frontoclypeal horn usually bears a pronounced inflection near base; the horn is elongate, with rounded to subtruncate apex. The antennal funicle has four antennomeres in which the first is shorter than the next three together. The pronotum is convex with a broadly rounded anterior edge. The anterior portion of each hypomeron has a slightly rounded outer edge. The tegmen has a narrow inner emargination at the apical edge which is less than one half of the total length of the tegmen; its outer edges bear an inflection at the first basal one half; each lobe of the apical portion has one small denticle at the inner apical edge and a slight notch on the outer portion. 14. Body glabrous, elongate, subcylindrical; dorsum mostly yellowish-brown; venter mostly reddish-brown; basal antennomeres and mouthparts yellowish brown; antennal funicle, tarsi and legs yellowish to reddish-brown; antennal club dark reddish-brown. Head barely visible from above; area immediately above horn base concave, glabrous, sparsely punctate; frontoclypeal ridge strongly produced forming a long, narrow median horn directed upwardly (in mm: length 0.29; basal width 0.28, Figure 3A, black arrow), laminate in lateral view ( Figure 3A, red arrow) and bearing several minute, sparsely distributed setae; horn with a pronounced lateral inflection near base (Figure 11.5, big black arrow) and a rounded, extended subtruncate apex (Figure 3A   Diagnosis. Each lateral contour of male frontoclypeal horn usually bears a pronounced inflection near base; the horn is elongate, with rounded to subtruncate apex. The antennal funicle has four antennomeres in which the first is shorter than the next three together. The pronotum is convex with a broadly rounded anterior edge. The anterior portion of each hypomeron has a slightly rounded outer edge. The tegmen has a narrow inner emargination at the apical edge which is less than one half of the total length of the tegmen; its outer edges bear an inflection at the first basal one half; each lobe of the apical portion has one small denticle at the inner apical edge and a slight notch on the outer portion. 14. Body glabrous, elongate, subcylindrical; dorsum mostly yellowish-brown; venter mostly reddish-brown; basal antennomeres and mouthparts yellowish brown; antennal funicle, tarsi and legs yellowish to reddish-brown; antennal club dark reddish-brown. Head barely visible from above; area immediately above horn base concave, glabrous, sparsely punctate; frontoclypeal ridge strongly produced forming a long, narrow median horn directed upwardly (in mm: length 0.29; basal width 0.28, Figure 3A, black arrow), laminate in lateral view ( Figure 3A, red arrow) and bearing several minute, sparsely distributed setae; horn with a pronounced lateral inflection near base (Figure 11.5, big black arrow) and a rounded, extended subtruncate apex (Figure 3A Figure 3B); distance between punctures about 4 to 5 puncture-widths; each puncture bearing a yellowish decumbent minute setae, barely visible even at a magnification of 150x; interspaces microreticulate. Scutellum small, subtriangular; BW 0.08 mm and SL 0.04 mm. Elytra about 1.8x as long as pronotum; sides subparallel at basal two-thirds, then abruptly converging toward apex; punctation single, similar to pronotal punctation but comparatively finer; vestiture similar to that of pronotum; humeral calli conspicuous. Metathoracic wings developed, apparently functional. Prosternum in front of coxae shallowly biconcave; prosternal process thin (Figure 3A lectotype and Figure 4A other specimen white arrow), parallel-sided, as long as coxae and projected below prosternal disc. Hypomera subglabrous and microreticulated, biconcave, anterior portion with outer edge slightly rounded ( Figure 11.5, small black arrow). Pro-, meso-and metathoracic tibiae as in the diagnosis of the furcifer group. Metaventrite microreticulate, moderately convex, subglabrous, bearing scattered slender setae; discrimen not discernible in this specimen. Abdominal ventrites microreticulate; punctation shallow; vestiture of scattered slender setae, longer than those on dorsum; length of ventrites I−V (in mm, from base to apex of each ventrite at the longitudinal midline): 0.16, 0.06, 0.07, 0.07, 0.07. First abdominal ventrite bearing a circular, marginated, pubescent sex patch at centre (Figure 3C lectotype and 4B other specimen, white arrow) with a transverse diameter of 0.03 mm in the lectotype specimen. Male abdominal terminalia (Figure 3D, lectotype) with posterior edge of sternite VIII bearing a deep, concave, mesal emargination ( Figure 3D, sternite VIII, black arrow); posterior corners sclerotised and rounded, bearing bristles; disc membranous; lateral edges diverging from posterior to anterior portion; anterior edge sublinear. Tegmen ( Figure 3D, teg and Figure 11.5, teg) with inner emargination of apical edge narrow and shallow, less than half total length ( Figure 11.5, teg, red dashed line); each lobe of the apical portion bearing one small denticle at the inner apical edge ( Figure 11.5, teg, black arrow) and a small notch on the outer portion ( Figure 11.5, teg, blue arrow); lateral edges with an inflection at the basal half ( Figure 11.5, teg, red arrow). Penis elongate, subcylindrical, basal edge blunt ( Figure 3D, pen, black arrows), sides subparallel along basal two-thirds and then gradually converging apically.
Females ( Figure 3F). Similar to males except for the following features: abdominal sex patch absent; anterior edge of head shallowly emarginated; frontoclypeal ridge devoid of horn.
Variation   Remarks. The names here synonymized with C. cornifer are of species described largely on differences in shape and length of the frontoclypeal horn of males and in dorsal coloration of individuals. However, a careful examination and comparison of specimens, especially of sclerites of male terminalia, showed that these differences represent intraspecific variation. In all examined populations of C. cornifer, the male frontoclypeal horn is extremely variable in length and even in shape. There are small male morphs with the apex of the frontoclypeal horn slightly bifurcated or truncated, intermediate morphs, and large morphs like the lectotype of C. cornifer ( Figure 5A-H). Small males with a small frontoclypeal horn slightly bifurcated at apex are relatively common (e.g., see the small horns in Figure 5C−F) but bifurcation in large males with large horns is rare (one case shown in Figure 5H). Some specimens from Ubá (MG, Brazil) and Grussaí (RJ, Brazil) have the lateral contours of pronotum angulate and the anterior edge forms two prominent lobes. The coloration in both sexes varies from yellowish-brown or reddish-brown, even in individuals from a single locality, to black (especially specimens of the southern tip of the distributional range) ( Figure 6A-C). The male specimen from Florida (EUA), previously identified as C. monocerus, was not measured due to its poor condition, except for its TL. Nevertheless, TL (1.18 mm), body shape and anatomy of male abdominal terminalia show that it is like the large morphs of C. cornifer from South American localities and is considered here to be a synonym of C. cornifer. Ceracis simplicicornis (Pic), also proposed as a new synonym of C. cornifer, was described as "nigro-piceus" ( Figure 6D) but we observed that it is just a colour variation in populations from Argentina and southern Brazil. The type-locality of both C. cylindricus, of which the type is lost, and C. simplicicornis is Buenos Aires. Having examined many specimens from southern South America, we concluded that the diagnostic features in the descriptions of both C. cylindricus and C. simplicicornis represent intraspecific variation of C. cornifer. Ceracis unicornis is an interesting case, before the revision of North American Ceracis by Lawrence [3], species described as Ceracis were those with eight antennomeres, while species described as Ennearthron were those with nine antennomres. Although C. unicornis was described as a Ceracis, it has nine antennomeres, which was first noted by Lawrence [3] and confirmed by us. Ceracis unicornis was described as "nigro-piceus", a colour variation common in other populations of C. cornifer, as pointed out above; it is another intraspecific variation and is here synonymized with it C. cornifer. The examined specimens from Campo Grande (MS, Brazil) resemble C. ruficornis, with the horn apex slightly bifurcated, body uniformly shiny black and legs with a somewhat amber colour, but a more careful examination and dissection of males allowed reliable identification as C. cornifer. Examined specimens from Paranhos (MS, Brazil) are also black ( Figure 6, VII). Aside from these colour variations, teneral forms, which are light colored, occur in all populations. Male terminalia of all dissected specimens of C. cornifer, including those from populations previously identified as C. monocerus and C. simplicicornis, are extremely similar, mainly in the shape of penis and sternite VIII. In the male specimen from Florida (EUA), the emargination on the outer portion of each lobe is more prominent than in specimens from Brazil. All observed variation in male terminalia was weak or inconsistent in a population or between populations, and was not consistent with the observed variation in body colour, and length and shape of the male frontoclypeal horn. Therefore no support could be found for maintaining C. cylindricus, C. monocerus, C. simplicicornis and C. unicornis as separate species.
Distribution. Ceracis cornifer is widely distributed in the southern, southeastern and southwestern Neotropical region, without records from the central and northern South America, but occurring in southwestern Mexico, in a few Caribbean islands and southern USA (Figure 2). This species is syntopic with C. furcifer in Paranhos (southwestern Brazil) and "Serra do Cipó" (locality of Jaboticatubas, southern Brazil). In these two samples, C. cornifer and C. furcifer were found living in the same basidiomes of P. sanguineus. Ceracis cornifer and C. ruficornis are also sympatric in three localities in southeastern Brazil (Paraty, Peruíbe and Ilha da Victória) (Figure 2).     Diagnosis. The apex of the frontoclypeal horn of males is elongate and emarginated at middle, forming two conspicuous lobes with rounded apex; the lateral contours of horn lack inflection near base, but in the largest morphs the horn is conspicuously narrowed at middle. The antennal funicle has three antennomeres, in which the first is equal or longer than the next three antennomeres together. The apical portion of tegmen has a short inner emargination, which is less than one half of the tegmen length; the lateral edges have an enlargement before apex, and the outer apical portion of each lobe bears a prominent inflection.

Ceracis furcifer
Redescription. Lectotype, here designated ( Figure  14. Body glabrous, elongate, subcylindrical; frontoclypeal horn mostly reddish-brown; dorsum, from apex of pronotum to elytral disc, dark reddish-brown; apical half of elytra, reddish-brown; venter mostly dark reddish-brown, except for the reddish-brown abdominal ventrites; basal antennomeres, funicle, mouthparts and legs yellowish-brown, but antennal club reddish-brown. Head barely visible from above; area immediately above horn base concave, glabrous and sparsely punctate; frontoclypeal ridge strongly produced forming a long horn directed upwardly, laminate in lateral view (in mm: length 0.3, basal width 0.3); horn apex elongate, emarginated at middle, forming two conspicuous rounded lobes ( Figure 7A, black arrow; Figure 11.4, big black arrow); lateral contours of horn without inflection near base, but conspicuously narrowed at middle (Figure 11.4, small black arrow). Antennae (right antennae measured) with FL 0.08 CL 0.14, CL/FL 1.75, length of antennomeres 1−8 (in mm) as follows: 0.06, 0.04, 0.04, 0.02, 0.02, 0.03, 0.05, 0.06; sensillifers barely visible. Eyes coarsely faceted, with minute slender yellowish in intersections of ommatidia; GW 0,11 mm. Pronotum subquadrate, with anterior portion produced forward, concealing head when seen from above; anterior edge slightly emarginated at middle, forming two small lobes; sides narrow, not visible from above; posterior edge sublinear; punctation fine, single, uniform and regularly distributed ( Figure 7B); distance between punctures about 2 to 3 puncture-widths; each puncture bearing a yellowish decumbent minute setae, barely visible even at a magnification of 150x; interspaces microreticulate. Scutellum small, subtriangular, with few punctures, each one bearing a short, fine decumbent setae; BW 0.08 mm and SL 0.05 mm. Elytra about 1.7x as long as pronotum; sides subparallel at the basal two-thirds, then abruptly converging toward apex; punctation single, finer than pronotal punctation; humeral calli conspicuous. Metathoracic wings developed, apparently functional. Prosternum in front of coxae shallowly concave; prosternal process thin ( Figure 7C, white arrow), similar to Cer. cornifer species ( Figure 4A) and parallel-sided, almost as long as coxae and projected Diagnosis. The apex of the frontoclypeal horn of males is elongate and emarginated at middle, forming two conspicuous lobes with rounded apex; the lateral contours of horn lack inflection near base, but in the largest morphs the horn is conspicuously narrowed at middle. The antennal funicle has three antennomeres, in which the first is equal or longer than the next three antennomeres together. The apical portion of tegmen has a short inner emargination, which is less than one half of the tegmen length; the lateral edges have an enlargement before apex, and the outer apical portion of each lobe bears a prominent inflection.
Females ( Figure 7F). Like males, but abdominal sex patch absent and frontoclypeal ridge devoid of horn. They resemble females of C. cornifer, but in the latter each antenna has nine antennomeres instead of eight.
Variation Remarks. We dissected the lectoypes of C. furcifer and C. semipallidus, compared their male genitalia and confirmed the synonymy proposed by Lawrence [3]. The shape of the frontoclypeal horn in males of C. furcifer is variable. However, its apex is usually bifurcated in small to large morphs ( Figure 5I,J). In small morphs, this bifurcation may be very prominent ( Figure 5J). The occurrence of more than one body colour among individuals from the same population is common ( Figure 8A) and the coloration "half brown, half dark-brown" seems to be one of the most common ( Figure 8A, arrow). There are populations in which individuals are homogeneously black ( Figure 8C, arrow), but other intermediate colorations can also occur (e.g., Figure 8B). The lobes of tegmen are rounded and comparatively larger in some males (e.g., specimens from Manaus, Brazil); in other cases, these lobes are conspicuously angulate (e.g., in a specimen from Antigua, Caribbean Sea).
Distribution. Ceracis furcifer occurs overwhelmingly incentral and northern South America, extending its range throughout the Antilles until Mexico (Figure 2). This species is syntopic with C. cornifer in Paranhos (southwestern Brazil) and "Serra do Cipó" (locality of Jaboticatubas, southern Brazil). In these two samples, C. furcifer and C. cornifer were found living in the same basidiomes of P. sanguineus. Ceracis furcifer is also syntopic with C. hastifer in San Luis de Palenque (Colombia) and these two species were also found living in the same basidiomes of P. sanguineus.  Diagnosis. The base of the frontoclypeal horn in males does not have lateral inflection and the horn is expanded until one third of its length. The antennal funicle has four antennomeres, the first being shorter than the following three antennomeres together. The anterior portion of hypomera has Diagnosis. The base of the frontoclypeal horn in males does not have lateral inflection and the horn is expanded until one third of its length. The antennal funicle has four antennomeres, the first being shorter than the following three antennomeres together. The anterior portion of hypomera has the outer edge broadly rounded. The lateral edges of tegmen are almost linear, without inflection; the apical portion bears a deep inner emargination at least two-thirds the length of tegmen, forming two long lateral lobes; the outer apical edges of lobes are apparently devoid of emargination.
Redescription. Lectotype, here designated ( Figure 9A-C,E) Dorsum mostly dark reddish-brown; venter mostly reddish-brown, except for yellowish-brown hypomera, legs and mouthparts. Head barely visible from above; area immediately above horn base concave, glabrous, sparsely punctate. Frontoclypeal ridge strongly produced forming a long, narrow median horn directed upwardly (in mm: length 0.5, basal width 0.32) ( Figure 9A, black arrow), laminate in lateral view ( Figure 9A, red arrow) and bearing several minute, sparse setae; horn largest at base and tapering until its basal one-third (Figure 11 Pronotum with anterior portion produced forward, concealing head when seen from above; anterior edge shallowly emarginated, forming two short and acute frontolateral lobes; sides narrow, not visible from above; posterior edge sublinear, punctation single, uniform and regularly distributed ( Figure 9B), with microreticulate interspaces; distance between punctures from about 1 to 3 puncture-widths; each puncture bearing a yellowish decumbent minute setae, barely visible even a magnification of 150x. Scutellum small, subtriangular, with few punctures, each one bearing a short, fine, decumbent seta; BW 0.09 mm and SL 0.04 mm. Elytra about 1.84x as long as pronotum; sides subparallel at the basal two-thirds, then abruptly converging toward apex; punctation single, finer than pronotal punctation; humeral calli conspicuous. Metathoracic wings developed, apparently functional. Prosternum in front of coxae shallowly biconcave; prosternal process thin ( Figure 9A, white arrow), similar to Cer. cornifer species ( Figure 4A) and parallel-sided, almost as long as coxae and projected below prosternal disc. Hypomera with outer edge of anterior portion broadly rounded. (Figure 11.5', small black arrow). Pro-, meso-and metathoracic tibiae similar to the ones of other furcifer group species (see the diagnosis of the furcifer group). Metaventrite moderately convex, subglabrous, microreticulate, bearing scattered slender setae; discrimen not discernible. Abdominal ventrites microreticulate, bearing shallow punctures and scattered slender setae longer than those on dorsum; length of the ventrites I−V (in mm, from base to apex of each ventrite at the longitudinal midline) 0.19, 0.05, 0.05, 0.06, 0.08. First abdominal ventrite bearing a circular, marginated, pubescent sex patch at the centre ( Figure 9C, arrow), similar to Cer. cornifer species (Figure 4B), with a transverse diameter of 0.06 mm. Male abdominal terminalia (in a paralectotype) ( Figure 9D) with the posterior edge of sternite VIII bearing a deep, concave, mesal emargination ( Figure 8D, sternite VIII, arrow); posterior corners rounded, sclerotised, bearing bristles; disc membranous; lateral edges diverging from posterior to anterior portion; anterior edge slightly biconcave. Tegmen ( Figure 9D, teg and 11.5', teg) with deep inner emargination at the apical portion, about two-thirds the length of tegmen ( Figure 11.5', teg, red dashed line); lateral edges almost linear, without inflections; outer edges near apex devoid of emargination. Penis elongate, subcylindrical, basal and apical portions membranous ( Figure 9D, pen, arrows); disc sclerotised; apical portion enlarged.
Females ( Figure 9F). Similar to males, except for being devoid of abdominal sex patch and horn at the frontoclypeal ridge. They mostly resemble females of C. cornifer, but are usually larger.
Variation. Males, measurements in mm (n = 6, included the lectotype) TL 1.14−1. Diagnosis. The male frontoclypeal horn has an expanded apex, slightly emarginated at middle forming two small rounded lobes. The lateral contours of the horn do not have inflection near base but the horn is slightly narrowed at middle. The antennal funicle has three antennomeres, the first equal or longer than the following three antennomeres together. The apical portion of tegmen has an inner emargination shallowly enlarged and less than one half of the length of tegmen; the lateral edges are expanded before apex, with a shallow inflection at the outer apical edge of each lobe.
Redescription. Plesiotype (Figure 10A−D).  4' Lateral contours of frontoclypeal horn straight from the basal third, usually devoid of lateral inflections (Fig 11.5', big black arrow); anterior portion of hypomera with outer edge broadly rounded (Fig 11.5', small black arrow); apical portion of tegmen with deep median emargination about two-thirds the length of tegmen (Fig 11.5', teg, red dashed line), lateral edges almost straight, without or with an inconspicuous inflection at the first basal one-third (Fig 11.5', teg, red arrow), less prominent than in C. cornifer, apical portion of each lobe without a denticle at the inner apical edge and without emargination at the outer edge….Ceracis hastifer Mellié Figure 11. Characters for the identification of males of the Ceracis furcifer species-group. See 3.2.5. Identification key above for explanations.

Discussion
Species in the furcifer group are very similar externally, even in the morphology of sclerites of male abdominal terminalia. However, there are two clear subgroups: (i) species with eight Diagnosis. The male frontoclypeal horn has an expanded apex, slightly emarginated at middle forming two small rounded lobes. The lateral contours of the horn do not have inflection near base but the horn is slightly narrowed at middle. The antennal funicle has three antennomeres, the first equal or longer than the following three antennomeres together. The apical portion of tegmen has an inner emargination shallowly enlarged and less than one half of the length of tegmen; the lateral edges are expanded before apex, with a shallow inflection at the outer apical edge of each lobe.
Females ( Figure 10E). Like males but devoid of abdominal sex patch and horn on head. They mostly resemble females of C. furcifer, but are usually homogeneously black.
Variation. Males, measurements in mm (n = 9, including the plesiotype) TL 1. Remarks. We examined photographs of the lectotype (e.g., Figure 10F). It differs from the specimens we had in our hands mainly in the anterior edge of pronotum, which is conspicuously emarginated instead of slightly emarginated as in the plesiotype. Specimens with the greatest pronotal width (PW) are the largest but smaller than the examined C. hastifer. Individuals of C. ruficornis are usually black, except for a single specimen from Paraty (Brazil-RJ), which is dark reddish-brown. As in other species of the furcifer group, the male frontoclypeal horn also varies in shape and length between morphs and, as in C. cornifer, the horn may be bifurcate at apex in small individuals with small horns ( Figure 5N). However, a bifurcate male horn is also common in large morphs ( Figure 5M), which is different from that observed in C. cornifer. The type locality of C. ruficornis is Blumenau (SC, Brazil), and in the examined material the closest locality was Peruíbe (SP, Brazil). However, specimens from Bertioga (SP, Brazil) were in better condition, so we used this for the redescription (one of them as a "plesiotype").
Distribution. Known only for a few localities close to the southeastern coast of Brazil, where it is sympatric with C. cornifer in Paraty (in the state of Rio de Janeiro), Peruíbe and Ilha da Victoria (in the state of São Paulo) (Figure 2).
1' Prosternal process thin but not laminate (Figure 11.2, white arrows); tegmen with a deep, longitudinal, apical emargination forming two parallel lobes with rounded or blunt apices (Figure 11.2, teg, black arrow) (furcifer group) . . . . 2 2 Antennal funicle with three antennomeres (Figure 11.3) . . . .3 2' Antennal funicle with four antennomeres (Figure 11.3') . . . .4 3 Apex of frontoclypeal horn usually widened and mesally emarginate, forming two conspicuous rounded lobes (Figure 11.4, big black arrow); lateral contours of horn without inflection near base but usually conspicuously narrowed at middle (Figure 11.4, small black arrow); tegmen with lateral edges widened preapically (Figure 11.4, teg, small red arrows), with a prominent inflection at the outer apical edge of each lobe (Figure 11.4, teg, big red arrows) . . . .Ceracis furcifer Mellié 3' Apex of frontoclypeal horn expanded but only slightly emarginated mesally, forming two small rounded lobes (Figure 11.4', black arrow); tegmen with lateral edges slightly widened preapically (Figure 11.4', teg, small red arrows) but with a shallow inflection at the outer apical edge of each lobe (Figure 11.4', teg, big red arrows) . . . .Ceracis ruficornis Pic 4 Lateral contours of frontoclypeal horn usually with a pronounced inflection near base ( Figure 11.5, big black arrow); anterior portion of hypomera with outer edge slightly rounded. Figure 11.5, small black arrow); apical portion of tegmen with narrow median emargination less than one half the length of tegmen (Figure 11.5, teg, red dashed line), outer edges usually with a conspicuous inflection at first basal one half (Figure 11.5, teg, red arrow), apical portion with each lobe bearing a small denticle at the inner apical edge (Figure 11.5, teg, black arrow) and a small and shallow emargination at the outer edge ( Figure 11.5, teg, blue arrow) . . . .Ceracis cornifer (Mellié) 4' Lateral contours of frontoclypeal horn straight from the basal third, usually devoid of lateral inflections (Figure 11.5', big black arrow); anterior portion of hypomera with outer edge broadly rounded (Figure 11.5', small black arrow); apical portion of tegmen with deep median emargination about two-thirds the length of tegmen (Figure 11.5', teg, red dashed line), lateral edges almost straight, without or with an inconspicuous inflection at the first basal one-third ( Figure 11.5', teg, red arrow), less prominent than in C. cornifer, apical portion of each lobe without a denticle at the inner apical edge and without emargination at the outer edge . . . .Ceracis hastifer Mellié

Discussion
Species in the furcifer group are very similar externally, even in the morphology of sclerites of male abdominal terminalia. However, there are two clear subgroups: (i) species with eight antennomeres (C. furcifer and C. ruficornis), in which males usually have the frontoclypeal horn incised at apex forming two lobes and the tegmen is widened before apex, with an inflection on both outer apical edges, (ii) species with nine antennomeres (C. cornifer and C. hastifer), in which the male frontoclypeal horn is usually truncate or shallowly emarginate apically and the tegmen is almost parallel-sided, with both outer apical lobes rounded and each bearing a shallow emargination on the outer edge. Below we discuss the observed intraspecific variation in species of the furcifer group, their geographic distribution based on data provided here and their specialization on the host fungus Pycnoporus sanguineus.

Intraspecific Variation: Coloration and Horn Shape in Males
There is more intraspecific variation in species of the furcifer group than previously observed, mainly in the shape of the male frontoclypeal horn, between males of the same or of different populations ( Figure 5). Another aspect is colour variation in populations of C. cornifer and C. furcifer (Figures 6 and 8). These variable traits were considered diagnostic for species of the furcifer group recognised before our work [1,[11][12][13]42,46]. Despite these differences, examination of sclerites of male abdominal terminalia, mainly the tegmen, revealed that the furcifer group comprises only four species, instead of eight as accepted before. Consequently, C. cornifer shows a disjunct geographic distribution and the greatest intraspecific variation among species of the furcifer group.
The use of body colour and shape of male frontoclypeal horn for delimiting ciid species has led to several synonyms (for example, see synonymy in Lawrence [3,47]). For instance, the species name C. semipallidus was a clear allusion to its light coloration (see Pic [46]), which is indeed a variation observed in C. furcifer. Therefore, the synonymization of C. semipallidus and C. furcifer proposed by Lawrence [3] is correct.
Differences in body coloration may well be a consequence of a relatively long period of time between emergence and attainment of full pigmentation, when teneral adults are abundant in ciid populations [3]. As overlap of generations is common in ciids, the consequence is that an established population may have adults with every degree of pigmentation, from recently emerged and thus light coloured (teneral) to fully pigmented adults. Although we did not test this, it would be an explanation for part of the observed body colour variation in furcifer group species (Figures 6 and 8).
However, we shall consider genetic and environmental factors together, which may determine body coloration. When coloration has a genetic basis, colour may also vary with environmental conditions, especially with temperature [48]. Individuals of C. cornifer from similar latitudes have different body coloration, being usually yellowish or reddish-brown ( Figure 6C). However, individuals of the southern tip of the distribution (in areas with the lowest mean temperatures; Figure 6A-B) are usually black (Figure 6C), being conspicuously different from those in northern latitudes. Interestingly Pic [13] described C. simplicicornis (a new synonym of C. cornifer proposed here) from Buenos Ayres as "nigro-piceus". This record represents precisely the most southern tip of the distribution and the area with the lowest mean temperature in our study ( Figure 6B,D).

Distribution Patterns of the furcifer Group
Species of the furcifer group do not overlap for most of their geographic distributional ranges ( Figure 2) but there are cases of syntopy and/or sympatry in a few localities (Figure 2). Ceracis cornifer is sympatric with C. ruficornis in three localities in the coast of Brazil and syntopic with C. furcifer in Paranhos, all these localities being in the Atlantic Forest biome, although Paranhos is very close to the Cerrado (Brazilian savanna) of Mid-West Brazil. Ceracis cornifer is also syntopic with C. furcifer in Serra do Cipó, a locality in the east limit of the Cerrado in Southeast Brazil, close to the Atlantic Forest biome. Ceracis hastifer and C. furcifer are syntopic in San Luis de Palenque (Colombian Savannah), and in Marabá (Amazon biome). Therefore, all syntopies observed by us are restricted to their distributional frontiers, which coincide with frontiers between biomes. Further studies shall evaluate whether the split of species of the furcifer group was related with the separation of the Atlantic and Amazon biomes. This event, which occurred in the Pliocene period, explains the currently distribution patterns of several organisms, e.g., mammals, birds, insects and plants [49][50][51][52][53][54][55] and is a plausible hypothesis to be tested for explaining the distribution patterns we show here.

Specialization on the Host Fungus Pycnoporus sanguineus
Although there are records of furcifer group in other fungi (see Table A2), they are mostly associated with P. sanguineus (Table A1). Aside from ciid beetles, few animals utilize basidiomes of P. sanguineus as food (Table A1). For instance, a colony of Acromyrmex lundi (Guérin, 1838) accepted basidiomes of P. sanguineus as food under laboratory conditions, although in the field it was observed harvesting basidiomes of Agrocybe [56].
The cases of consumption of P. sanguineus by humans were isolated and regard principally to South American indigenous tribes [57][58][59], which use P. sanguineus as medicine, e.g., for treating against aphtha or insolation, in both cases diluting basidiomes in water and drinking [58]. Fidalgo and Hirata [57] studied the names and uses given to P. sanguineus in three Brazilian indigenous tribes from the Xingu National Park, state of Mato Grosso. In only one of these indigenous tribe (Txucarramãe) there were reports of people eating P. sanguineus. Humans use basidiomes of P. sanguineus in the early decay stages [60,61], in which they are powdered and, when used to treat mouth infections, directly applied to the affected area. When basidiomes begin to turn white, they become highly toxic [61], due to toxic elements and heavy metals absorbed by basidiomes, e.g., cadmium [62]. Basidiomes of P. sanguineus also have high concentration of cinnabarins, toxic substances with antibiotic action [10,26]. Such high toxicity can function as a barrier for consumption by organisms. However, the use of P. sanguineus by ciid beetles suggests that they may be resistant to antibiotic and toxic compounds of this fungus [10]. Populations of C. cornifer can colonize basidiomes of P. sanguineus before they begin to sporulate [9], when levels of toxic substances are low. However, the population increases and individuals continue feeding when basidiomes become more toxic in advanced decay stages. Here, the number of records in P. sanguineus (mainly breeding records) demonstrates that the furcifer group constitute the only truly specialized animals feeding on basidiomes of P. sanguineus. Therefore, these beetles perform a great environmental service, removing basidiomes of P. sanguineus, which would persist in nature for years.
One of the ecological bases for evolution of specialization is environmental constancy [63]. The use of a single fungus as resource might have put the furcifer group in an evolutionary stasis: in all areas occupied by their populations, they use the same resource, which is widely available in most open areas in the Neotropical region. On the other hand, populations of polyphagous species can undergo subsequent specialization, becoming oligophagous or even monophagous, which may act as evolutionary constraint and lead to rapid radiation. For instance, that was possibly the case for polyphagous ciid species of the Ceracis cucullatus group [5,6] and also of the Cis taurus group [19]. In both C. cucullatus and Cis taurus groups, there are a few widespread polyphagous species and several geographically restricted oligophagous ones [4,6,10,19]. The evolutionary stasis of the furcifer group is a hypothesis that may explain why disjunct populations of C. cornifer have not undergone speciation, or at least evolution has not lead to conspicuous morphological differences in individuals of disjunct populations.

Conclusions
The furcifer group now encompasses four species: C. cornifer C. hastifer, C. furcifer and C. ruficornis. The male frontoclypeal horn and body coloration in these species have great intraspecific variation; therefore, these are not good diagnostic features. We concluded that examination of sclerites of male terminalia is the most accurate way to identify species of the furcifer group. We show that the furcifer group are widely distributed along the Neotropical region and constitute the only specialized animals that feed on basidiomes of P. sanguineus.
Appendix A   Table A1. List of animals feeding on basidiomes of Pycnoporus sanguineus. The numbering of each morphospecies cited below is the same used in the corresponding source.