Parallelodemas Faust from South China ( Coleoptera , Curculionidae , Baridinae ) , with notes on sexually dimorphic characters

Nine species of Parallelodemas Faust are reported from China. In addition to the previously recorded P. impar Voss, we found P. docile Faust, P. vicinum Faust and the following six species newly described herein: P. dimetans sp. n., P. feae sp. n., P. petilum sp. n., P. plumosum sp. n., P. setifrons sp. n. and P. tumens sp. n. Parallelodemas tarsale Voss from Java is transferred to Lepidomyctides Yoshihara and Morimoto (comb. n.). Lectotypes are designated for P. docile, P. imperfectum Faust, P. perfectum Faust, P. tardum Faust and P. vicinum. Several morphological modifications with unknown functions are documented, illustrated and discussed. Males of some species have special setae on rostrum, antennal scape and mesotarsus. A medially notched epistome apparently occurs in both sexes but seems to wear off in females, probably during the preparation of oviposition sites. The mandible is unusual in having a convex, edentate inner face and incisor-like structures on the outer face. Key Words


Introduction
Among the currently accepted 548 genera of baridine weevils, Parallelodemas Faust is notable for having numerous morphological peculiarities.Faust (1894) noticed modified setae on the male mesotarsus of two of his five species and a loss of the two distal tarsites in another [actually present but minute].Voss (1941) commented on the basally bifurcate prosternum of female P. impar Voss, and Marshall (1945) and Morimoto and Yoshihara (1996) on apparently abducent mandibles.To this one may add the frequently worn female epistome and marked sexual dimorphism of further body parts, such as rostrum, antennal scape and eye, in at least some species.However, this interesting genus is taxonomically challenging because of great morphological similarity of the species, pronounced sexual dimorphism and scarcity of material in collections.China is presently the only country with noteworthy collections of Parallelodemas.In this paper, we revise the Chinese species and document taxonomically important characters of the genus.
University, Zhejiang, China (ZAFU) and Zoological Institute of the Russian Academy of Sciences, St. Petersburg, Russia (ZIN).The above codens are used to refer to collections in the text.A total of 154 specimens was examined.Faust returned approximately half of the type series of his newly described species to L. Fea (the owner) and shared the rest with L. v. Heyden.Whenever possible, we designated as lectotype a male from the material returned to Fea and ignored the unpublished designations in Faust's retained material, which were made by museum staff subsequent to the acquisition of his collection.
If not provided on the label, coordinates of collecting sites were determined with GoogleEarth.Approximate collecting sites of Fea's specimens, from his 1885-89 journey to Myanmar, were estimated based on his travel itinerary (Vinciguerra 1890;Fea 1896).Descriptions are structured hierarchically, i.e., constant generic characters are not repeated in the descriptions of species.We found no evidence for a species with a sexually dimorphic epistome.However, the female epistome apparently wears off so we described it only for the male.Measurements of length were taken with an ocular micrometer in a stereomicroscope.Total length was measured from the anterior margin of eye to the abdominal apex in dorsal view.Length-width ratios of the penis are approximate values which do not take into account curvature.Illustrations were prepared from images taken with a Micropublisher 5.0 RTV digital CCD camera mounted on a Zeiss Ste-REO Discovery V12 or a Canon EOS 650D on a Leica DM2500 compound microscope.Aldus Freehand was used for vector graphics and Adobe Photoshop for pixel-based artwork.All genitalia illustrations were prepared from specimens collected in China.Explanations for morphological terms can be found at http://weevil.info/ glossary-weevil-characters.Our weevil classification follows Oberprieler et al. (2014) except that we maintain Baridinae and Ceutorhynchinae as separate subfamilies.
Diagnosis.Species of Parallelodemas can be recognized by characteristically elongate body (Fig. 1), medially notched epistome (which often is worn in females) and exodontous mandibles with evenly convex inner face (Fig. 3).Superficially, they resemble species of the conoderine subtribe Phaenomerina (see Morimoto 1961), but those have incrassate, ventrally dentate femora and larger eyes.The characters on the mandible and epistome separate Parallelodemas from certain grass-and sedge-associated, primarily Palaeotropical Baridinae with similarly slender rostrum and elongate body.The latter complex includes Eumycterus Schönherr, 1838; Trephognathus Marshall, 1945;Neosharpia Hoffmann, 1956;Caenobaris Nasreddinov, 1980;Lepidomyctides Yoshihara & Morimoto, 1994 and several species currently placed in other genera.Misplaced species.Yoshihara and Morimoto (1994) recognized that Parallelodemas tarsale Voss, 1937 is a species near Eumycterus and Lepidomyctides but they had very little material of those genera.We studied five Oriental species near P. tarsale (BPBM, IZCAS, SNSD, ZIN) and several species of Caenobaris, Eumycterus, Neosharpia and Trephognathus Marshall from Africa, Central Asia and India.While Eumycterus and its probable synonym Trephognathus can be distinguished by vertically moving mandibles (Marshall 1945;Korotyaev 2002), we were unable to recognize or to confirm the generic limits of the remaining species.We transfer here P. tarsale to Lepidomyctides in the widest sense, as Lepidomyctides tarsalis (Voss), new combination.
Redescription.Habitus: Total length 3.0-7.8mm, width 0.8-2.2mm; body slender subcylindrical (Fig. 1); integument black or brown, appendages and ventrites sometimes rufous; vestiture uniform or locally condensed to short vittae, setae either simple, squamiform, scalloped, deeply split or plumose.Head: Subspherical, contour often slightly warped at rostral base; eyes large, slightly encroaching on rostrum, bulging or flush with head contour, dorsally separated by width of rostrum at base; frontal fovea small to moderate; rostrum moderately elongate and slender, slightly curved, female with apical portion slightly inflated (Fig. 2); epistome produced and more or less notched, often worn off in females (Fig. 3); scrobe laterally descending, antenna inserted between midlength and apical fourth; funicle with 7 desmomeres; club compact, spindle-shaped, basal article approximately as long as remainder of club, not annexed to distal desmomere; mandibles with apparently abducent movement (away from center line and slightly ventrad), outer face with 1 large and 1-2 small secondary teeth, inner face convex and without teeth (Fig. 3).Prothorax: Barrel-shaped, elongate, nearly as wide as elytra.Anterior margin of pronotum not projected over frons, subapical constriction absent; basal margin bisinuous to accommodate projecting base of elytron; postoccular lobe feeble or absent.Prosternum without median channel, rarely slightly depressed in front of coxae; subapical constriction slight to moderate; basal lobe partially projected over mesosternum, with basal margin bifurcate or (rarely) truncate.Pterothorax: Mesoscutellum visible, trapezoid to subquadrate.Mesosternum unmodified.Mesepimeron smaller and narrower than mesepisternum, ascending between pronotum and elytron and visible in dorsal view.Metasternum medially depressed in male, flat or convex in female.Elytra: Elongate, sides subparallel, apices rounded individually, humerus developed, subapical callus feeble or absent, base at interstriae 3-6 slightly depressed and somewhat projected; striae 10, narrow but distinct, strial punctures not or slightly affecting edge of interstriae, strial setae absent; interstriae flat, punctate to transversely rugose, interstrial setae uniform or heterogeneous, modified setae restricted to basal and submedian vittae if present.Hindwings: Fully developed, length-width ratio 3.4-3.7,fore margin basally concave, anal lobe moderate, hind margin with setal fringe; venation agreeing with modal arrangement of subfamily (Zherikhin and Gratshev 1995).Abdomen: Ventrites unmodified, not or indistinctly sexually dimorphic.Sclerolepidia small to medium-sized, densely packed, digitate.Stridulatory devices absent.Male genitalia and associated structures: Tergite VII without plectra for stridulation; tergite VIII shorter than wide, distally without transverse carina; sternite VIII laterally with sclerotized pyriform area, medially desclerotized; sternite IX variously strongly curved, distal prongs narrowly to widely diverging but always symmetrical; penis dorsoventrally depressed, longer than basal apodemes; internal sac extending approximately to midlength of apodemes when inverted, with sclerite at insertion of duct or with pigmented flagellum; tegmen with ring dorsally closed, basal apodeme obsolete, parameroidal lobes developed.Female genitalia and associated structures: Tergite VII longer than wide, without transverse carina, setal vestiture squamiform basally and piliform distally, plectra for stridulation absent; sternite VIII distally forked into weakly sclerotized, widely dilated, U-shaped arms; hemisternite pigmented, stylus 1.9-2.2×as long as wide, distal setae half as long as stylus; bursa pouch-like, half as long as vagina; spermatheca sclerotized, collum short, often somewhat bulbous, ramus inserted on outer face of collum (facing away from cornu), rudimentary to long; spermathecal duct unpigmented, at most slightly longer than spermatheca, inserted distally in bursa.Legs: Procoxae separated by less than 1/3 diameter of coxa; pro-and mesofemora clavate, hindfemur less expanded and often partially sulcate ventrally; tibiae straight to curved (depending on ventral profile of femur), ventrodistal spine spiniform, robust and large on pro-and mesotibiae but somewhat smaller on metatibia; tarsus with 5 segments, third with anterior margin faintly to deeply excised, fifth long to greatly reduced, claws flat and basally fused, or miniaturized and medially fused to single blade.
Diversity and distribution.With the six new species described in this study, Parallelodemas includes now a total of twelve.The scarce material gives an unrepresentative picture of the distributional ranges of individual species.Species of Parallelodemas have been found  in China, India, Laos, Malaysia, Myanmar, Taiwan and Vietnam.Their distribution is primarily Oriental but several reach the Palaeartic part of China, northward up to Shaanxi and Zhejiang.
Biology.The host plant of Parallelodemas apparently is unknown.One specimen of P. docile is labeled as being taken from Buttontree, Anogeissus acuminata (Roxburgh ex Candolle) Guillemin et al. (Combretaceae).Other specimens were swept from low vegetation.Females with fully developed eggs occur from late April to early June.
Sexual dimorphism.Rostrum.Species of Parallelodemas exhibit marked sexual dimorphism of characters on the rostrum.Females generally have a longer and smoother rostrum than males, with a more basally inserted antenna and slightly inflated apical portion (Fig. 2).Gender-related differences in the basal width of the rostrum (Fig. 8) are apparent but often inconspicuous.The ventral side of the rostrum is setose in male P. impar, P. petilum and P. plumosum.However, the most striking difference, the length and shape of the epistome, may be acquired secondarily rather than being truly sexually dimorphic.Nearly all examined males have a projected, medially notched epistome, whereas it is almost always short and truncate in females (Fig. 3).However, the presence of projected epistomes in some female P. feae, P. impar, P. imperfectum and P. setifrons suggests a secondary loss, probably through abrasion during the preparation of oviposition sites, because the distally divergent mandibles afford no protection of the epistome as in other weevils.However, this needs to be confirmed with freshly emerged specimens and field observations.
Antenna.Males generally have a longer scape than females (usually as long as the funicle).The distal margins of the male scape can be setose, such as in P. impar (Fig. 2).
Mandible.At a first glance, it appears as if Parallelodemas has swapped the left with the right mandible or rotated them by 180 degrees (Fig. 3).The inner face not only lacks any trace of incisors, it also is evenly convex from base to apex and seems therefore dysfunctional.Moreover, the outer face is concave and armed with two apparently ordinary incisors, just like the inner mandibular face of most baridine weevils.However, three landmarks on the mandible leave no doubt that the seemingly abducent mandibular movement evolved by reversing the function of the abductor and adductor tendons rather than by rotating the mandible, a trend seen in some weevils with a very slender rostrum (Marshall 1945): (1) The dorsal and ventral mandibular sockets (preartis and postartis) are formed and located as in other Baridinae; (2) the mandibular setae are located on the outer face (between the basal incisors); and (3) the pharyngeal process is attached to the inner basal angle of the mandible.From this it follows that the incisors on the outer face are secondarily evolved structures and analogous to the inner incisors of other weevils.Morimoto and Yoshihara (1996) suggested an inversion of the mandibular movement from adducent to abducent.The laterally deeply excised mandibular articulation and widely divergent mandibles in many mounted specimens support this conclusion.Unfortunately, we could obtain neither direct field observations nor fresh specimens for scanning the abductor and adductor tendons.
Eye.While almost all Baridinae have eyes that are flush with the head contour, they are protruded in several Parallelodemas species.The eyes of male P. setifrons protrude more than those of females (Fig. 8), but the dorsal and ventral distance between them and their circumference are not affected.The increased eye surface affords more facets in the male but facet diameter is the same.
Leg. Several Parallelodemas species have large, deviant setae on the mesotarsus which crowd toward the distal (outer) half.These setae are arranged asymmetrically on the fifth (claw-bearing) tarsite and are much larger and more numerous in males than in females (Figs 6, 7).The individual tarsites, in particular the fifth, are often more elongate in males than in females.Males often have faintly thicker pro-and mesofemora than females.
Tergites.Like in other Baridinae, the eighth tergite is developed in males but internalized in females.Because the distal external tergite protrudes beyond the elytral apex well enough to expose the suture between the seventh and eighth tergites in males, this character is very useful for sexing specimens.
Ventrites.The male metaventrite is medially depressed and, together with the first abdominal ventrite, may have less setae than the female's.Voss (1941) mentioned a sexually dimorphic basal process on the prosternum of P. impar, but he either had a mixed series or his observation was incorrect.Diagnosis.This small species can be recognized by the presence of slender, bi-or trifid setae on the thoracic ventrites and ventrally glabrous male rostrum.Parallelodemas petilum is the only other known species with such setae but the male rostrum is hirsute.Description.Length 3.6-4.3mm, width 1.0-1.2mm; integument dark brown, antenna, tarsus, apex of female rostrum and often other parts of leg brown or rufous; ventral side and pygidium with simple, slender setae, thoracic sterna also with bi-and some trifid setae, basic vestiture of fine setae on pronotum and elytron, somewhat larger white setae at base of elytral interstria 3 and postmedially on interstriae 3 and 4; eyes slightly bulging; frons and base of rostrum with some recumbent setae; male rostrum 1.07× as long as pronotum, ventrally without setae, prorostrum 0.41-0.42×rostral length, slightly spatulate and apically diverging in dorsal view, epistome slightly notched, antennal scape with a few long setae, club 1.7× as long as wide; female rostrum 1.02-1.11×as long as pronotum, prorostrum 0.47-0.51×rostral length; prosternum gradually sloping in front of coxa, basal lobe notched; all femora hirsute ventrally; tarsus with tarsite 3 relatively small and excised to basal third, tarsite 5 shorter than 2+3 and distinctly protruding beyond anterior margin of 3, male mesotarsus with long, distally pointed setae; penis 2.5× as long as wide, apex roundly narrowed and slightly projected medially (Fig. 12), internal sac with harpoon-like sclerite and small sclerotized area near duct; spermatheca with nodulus and ramus short (Fig. 21).Diagnosis.Our material includes seven small specimens from three sites (3 Shaanxi, 1 Sichuan, 3 Vietnam), which form a close-nit complex of probably three species.They have bulging eyes, thoracic ventrites with bifid setae, a ventrally setose male rostrum and a slender penis with very long flagellum.Differences occur in the apical shape of the penis (Shaanxi -triangular; Sichuan -narrowly rounded; Vietnam -slightly projected) and the first abdominal ventrite (Vietnamese specimens with a pair of tubercles between the metacoxae).We describe the three specimens from Shaanxi as P. petilum and informally assign to this complex the four others.Similar species are P. dimetans (with nearly flush eyes) and P. setifrons (with plumose setae).
Distribution.The species (in the strict sense) is known from the Chinese province Shaanxi.
Material Diagnosis.This species can be distinguished from P. setifrons, the other known species with plumose setae, by glabrous frons and slightly protruding eyes in both sexes.Parallelodemas dimetans and P. petilum have at most trifid setae.
Distribution.The species occurs in China (Fujian, Hainan) and Taiwan.
Distribution.The species is known from China (Fu jian, Guangdong, Guizhou, Hunan).
Distribution.The species is known from China (Yunnan) and Myanmar.
Diagnosis.This species can be recognized by its characteristic tarsus: the enlarged third tarsite is barely excised anteriorly and the fifth is greatly reduced (Fig. 5).Parallelodemas docile has a larger fifth tarsite and is more elongate.
Distribution.The species is known from one site in Myanmar.
Distribution.The species is known from China (Sichuan, Yunnan, Zhejiang) and Laos.The record from Guatun in Fujian, by Voss (1956), applies to P. setifrons.
Diagnosis.Two of the eight known species with undivided setae have an unmodified male mesotarsus, i.e., they lack special setae and the fifth tarsite is not enlarged.One is P. tardum described from Myanmar, the other is P. tumens from China.Parallelodemas tardum is larger than P. tumens (5.4-6.6 mm vs. 3.8-4.8 mm) and has a shorter rostrum with a more distally inserted antenna.The females may be distinguished by body length.A difference between female P. perfectum and P. tardum is not apparent (each with one known specimen).Female P. feae are very similar but have ventrally hirsute femora.Redescription.Length 5.4-6.6 mm, width 1.6-1.9mm; integument black; ventral side and pygidium with undivided setae, basic vestiture of fine setae on pronotum and elytron, moderately wide white setae at base of elytral interstria 3 and postmedially on interstriae 3-5, on metepisternum and basolateral angles of pronotum; eyes flush with head contour; frons and base of rostrum glabrous; male rostrum 0.89-0.94×as long as pronotum, ventrally without setae, prorostrum 0.32-0.33×rostral length, apically slightly diverging in dorsal view, epistome short and slightly notched, antennal scape glabrous, club 1.8× as long as wide; female rostrum 1.04× as long as pronotum, prorostrum 0.50× rostral length; prosternum slightly tumescent in front of coxae (apparently not in female), basal lobe notched; pro-and mesofemora ventrally with erect squamiform setae; tarsus with tarsite 3 of moderate size and excised to basal third, tarsite 5 slightly longer than 3 and distinctly protruding beyond anterior margin of 3, male mesotarsus without specialized setae; penis 2.3× as long as wide, apex lancet-shaped and broadly rounded (as P. tumens, Fig. 18), internal sac with 2 small sclerites (hook and paired hook); spermatheca with collum bulbous, ramus short, nodulus obsolete (as P. dimetans, Fig. 21).
Distribution.Besides the type series from Myanmar, we have seen one female from India that might be this species.

Parallelodemas tumens Prena & Zhang, sp. n.
http://zoobank.org/2295F76C-0867-4E0C-980C-1CFB6E45ACE0 Diagnosis.Besides P. tardum, this is the only known species without split setae on the metepisternum and without a modified male mesotarsus.Parallelodemas tumens is smaller (<5 mm) than P. tardum and has a longer rostrum with a more basally inserted antenna.Differences in the genitalia are not apparent.Female P. tumens may be distinguished from female P. perfectum and P. tardum by smaller body size.All three species have specimens with a more or less tumescent prosternum.
Description.Length 3.8-4.8mm, width 1.1-1.3mm; integument black, antenna, tarsus, apex of female rostrum and often other parts of leg brown or rufous; ventral side and pygidium with undivided setae, basic vestiture of fine setae on pronotum and elytron, moderately wide white setae at base of elytral interstria 3 and postmedially on interstriae 4 and 5, on thoracic flank and basolateral angles of pronotum; eyes flush with head contour; frons and base of rostrum glabrous; male rostrum 1.06-1.08×as long as pronotum, ventrally without setae, prorostrum 0.41-0.42×rostral length, slightly spatulate and apically diverging in dorsal view, epistome short and truncate, antennal scape glabrous, club 1.8× as long as wide; female rostrum 1.20× as long as pronotum, prorostrum 0.53× rostral length; prosternum tumescent in front of coxae, basal lobe notched; pro-and mesofemora hirsute ventrally; tarsus with tarsite 3 of moderate size and excised to basal third, tarsite 5 slightly longer than 3 and distinctly protruding beyond anterior margin of 3, male mesotarsus without specialized setae; penis 2.5× as long as wide, apex lancet-shaped and broadly rounded (Fig. 18), internal sac with 2 small sclerites (hook and paired hook); spermatheca with nodulus and ramus short (as P. dimetans, Fig. 21).
Distribution.The species is known from the Chinese province Guizhou.
Etymology.The name is a participle presence active of tumeo (=to inflate, to distend; Latin).Diagnosis.From other species with undivided setae, P. feae can be separated by having ventrally hirsute femora and nearly flush eyes.Female P. tardum and P. tumens are very similar but have shorter and wider setae on the pro-and mesofemora.

Diagnosis.
A generally useful character for recognizing P. vicinum is the presence of imbricate squamiform setae on the distal half of the metepisternum.Parallelodemas docile has similar vestiture on the distal two thirds and an enlarged third tarsite.Small P. vicinum with more widely spaced setae on the metepisternum differ from the otherwise very similar P. perfectum by the apically truncate aedeagus and less curved female rostrum.These two and P. feae, a species with ventrally hirsute femora, are the only known species with undivided setae, flush eyes and clavate setae on the male mesotarsus.Redescription.Length 6.4-7.8 mm, width 1.6-2.2mm; integument black, teneral specimens with ventrites and legs partially dark rufous; ventral side with undivided setae, basic vestiture inconspicuous on pronotum and elytron, imbricate white squamiform setae at base of elytral interstria 3, postmedially on interstriae 3 and 4, on dorsal apex of mesepimeron, distal half of metepisternum, flank of prosternum, ventral face of pro-and mesofemora, dorsal face of metafemur and occasionally on basolateral angles of pronotum; eyes flush with head contour; frons and base of rostrum glabrous; male rostrum 1.06-1.15×as long as pronotum, ventrally without setae, prorostrum 0.36-0.38×rostral length and spatulate in dorsal view, epistome very slightly notched, antennal scape with long, cupreous setae, club 1.6× as long as wide; female rostrum 1.14-1.24×as long as pronotum, prorostrum 0.57-0.58×rostral length; prosternum gradually sloping in front of coxa, basal lobe notched; pro-and mesofemora ventrally with slender (male) or squamiform (female) setae; tarsus with tarsite 3 relatively small and excised to basal third, tarsite 5 as long as 2+3 and distinctly protruding beyond anterior margin of 3, male mesotarsus with moderately long, clavate, outward directed setae; penis 2.5× as long as wide, apex bottle-shaped (Fig. 9), internal sac with thick, tubular, basally curved sclerite; spermatheca with nodulus long and usually perpendicular to collum, ramus similarly long (as Fig. 27).
Distribution.The species is known from China (Yunnan), India and Myanmar.

Diagnosis.
Only two specimens of the sexually dimorphic P. perfectum are known, one of each gender.The species forms a complex with P. feae, P. tardum, P. tumens and P. vicinum, all of which have flush eyes, thoracic ventrites with undivided setae and a male mesotarsus with outward-directed clavate setae (Fig. 6).The profemur of the male P. perfectum is ventrally more expanded than in the other species.Parallelodemas feae has ventrally  hirsute femora; P. tardum has a shorter male rostrum; P. tumens is smaller (<5 mm); P. vicinum usually has denser vestiture on the mesepisternum and a less curved female rostrum.The few available female P. perfectum and P. tardum could not be distinguished with confidence.
Distribution.The species is known from one site in Myanmar.

Discussion
Species of Parallelodemas display an unusually diverse and complex suite of deviant morphological structures.Several occur in only a few species, such as the enlarged third tarsite or the deeply split setae on the ventrites.Others are male-specific, such as the setal fringes on rostrum, scape and mesotarsus, or the tubercles found on the first ventrite of an undescribed species near P. dimetans.The structural heterogeneity is increased further by the apically exposed epistome that often is worn off in females but rarely in males.Most of these traits can be found also in other tropical weevils, particularly in Dryophthorinae and Baridinae (Davis 2009;Anderson et al. 2014;Prena et al. 2014), although not as accumulated as in Parallelodemas.Very little is known about their functions and the few available observations may not always be transferable to other species.
It is long-known that numerous weevil species lack incisors on the mandible (Lacordaire 1865;Ting 1936;Günther 1938).In some cases, the mandible moves almost vertically rather than transversely opposed as in most other beetles (Horn 1873;McClenahan 1904;Marshall 1945;Morimoto 1962;Pelsue and O'Brien 2011).However, distally diverging mandibles with a convex inner face and incisor-like structures on the outer face are uncommon.They occur in several Dryophthorinae, such as Cyrtotrachelus Schönherr, Macrocheirus Schönherr, Otidognathus Lacordaire, Protocerius Schönherr, Rhinostomus Rafinesque and, among the Baridinae, in Parallelodemas and some Geraeus Pascoe (Casey 1922;Vaurie 1970;Morimoto and Yoshihara 1996).Many Rhynchitinae (Attelabidae) and some Cholini, Erirhinini, Tychiini and Platypodinae (Curculionidae) have similar exodontous mandibles (Ting 1936;Hamilton 1990;Thompson 1992) but with normal interior incisors and decussate apices.Three functions have been attributed to exodontous mandibles.Daanje (1964) was the first to point out that they occur in Rhynchitinae that pupate in soil but not in Attelabinae that pupate in leaf rolls.He concluded that the exterior tooth supports the weevil's emergence to the surface.Depending on the species group, the teeth are sheared off after emergence of the beetle or are retained in one or both sexes (Daanje 1964;Dieckmann 1974;Riedel 2014).A second function of the exterior tooth is its usage during the preparation of the leaf roll in some Rhynchitinae (Daanje 1964(Daanje , 1975)).A third possible function is related to oviposition.Kissinger (in litt., quoted by Vaurie 1970) conjectured that the exterior tooth might be used for making oviposition holes, by rip- ping through fibrous tissue of the monocotyledonous host plant.Eberhard (1983) observed that female Rhinostomus barbirostris (Fabricius) chew the oviposition hole and then withdraw the rostrum with a series of sharp jerks.The exodontous mandible may serve during the latter action for enlarging or cleaning the hole.While the mandibles of the above-mentioned dryophthorines have a thick, excavated outer face (Vaurie 1970), they are thin and blade-like in the baridines.It is conceivable that female Parallelodemas employ the outer face for ripping and cutting through plant tissue as suggested by Kissinger, perhaps on culms hollow inside or filled with pith, but chewing is necessary to at least initiate the oviposition hole.Our own observations showed that baridines without incisors are primarily pollen feeders and use their mandibles like pincers.Oviposition behavior has not been documented so far for any baridine with exodontous mandibles.The worn epistome of many female Parallelodemas may or may not be related to the aberrant morphology and movement of the mandible.Even though the epistome of Rhinostomus species is similarly exposed and unprotected as in Parallelodemas, we found no sign of wear in female R. barbirostris and R. niger (Drury).However, similar wear is apparent in female Apostasimerus serrirostris Boheman, a palm-associated Neotropical baridine with straight incisor area.
Gender-specific setae or setal patches occur relatively frequently on tibiae and ventrites of weevils (Eberhard 1983;Lyal 1993;Schat et al. 2007) but are less common on the rostrum.Short fringes or fuzzy patches occur for instance in Datonychus Wagner, Mogulones Reitter (Dieckmann 1972), Metamasius Horn (Vaurie 1968(Vaurie , 1970) ) and Pterocolus Say (Hamilton 1998).We noticed long setal fringes, like those present on the ventral rostrum of some male Parallelodemas species, in male Acythopeus barbatus Pascoe, Conoproctus longipes (Casey), C. quadripustulatus (Fabricius), Mycterus barbirostris Pascoe and M. imberbis Lea (probably a synonym of the former; all Baridinae).Observations on the usage of these setae are available only for one species of Rhinostomus, the "bottle brush weevil".Eberhard (1983) described how male R. barbirostris gently wipe the rostrum on the female's pronotum and elytron thereby apparently pacifying or immobilizing their chosen mate.Because this did not explain the presence of setae on the dorsal side of the rostrum, the author speculated that other sensory functions may be involved.However, his observations provided evidence that the setae have a behavioral, mating-related function.
If and how this applies to the exterior setae on the fifth mesotarsite of some male Parallelodemas species remains unknown.Similar setae occur in other weevils on the interior (proximal) face of the basal three tarsites or all around, particularly on the protarsus, but not on the exterior face of the fifth.
The weevil tarsus typically is cryptopentamerous (with a miniaturized fourth tarsite) but there are a few exceptions and numerous modifications.The fourth and fifth tarsites are lost in species of genera such as Anoplobaris Morimoto and Yoshihara, Anoplus Germar, Atelicus Waterhouse, Diabathrarius Schönherr, Macrobaris Champion, Syarbis Pascoe and Viticis Lea, and are greatly reduced in several others.An enlarged third tarsite is particularly common in African Dryphthorinae (e.g., Belorhynus Guérin-Méneville, Ichthyopisthen Aurivillius, Korotyaevius Alonso-Zarazaga and Lyal) and American grass-associated Baridinae (e.g., Macrobaris, Nertinus Voss, Trachymeropsis Champion).In many cases, the enlargement of the third tarsite is accompanied by a reduction of the fifth.Many if not all of these species live on swaying parts of their host plants and it is perceivable that the adhesive strength of the tarsus is increased by enlarging the surface of individual tarsites.
Although the structural diversity of these predominantly tropical weevils is appealing for morphological and behavioral studies, systematic fieldwork is greatly hampered by the still prevailing paucity of taxonomical and ecological information.Even the functions of rather ubiquitous structures, like the "prosternal horns" (Davis 2009;Davis and Engel 2010) present in Anthribidae, Nemonychidae and the curculionid subfamilies Baridinae, Conoderinae, Curculioninae and Molytinae, have remained largely unknown or were interpreted as being generally indicative for ritual fighting, even though the latter usage has been observed in just one species (Eberhard and Garcia 2000; own observations) while similar structures have other functions (Lacordaire 1863, p. 5;Lesne 1899, p. 143;Wood 1969, p. 43;Daanje 1975, p. 288;Thompson 1992, p. 869).It is our hope that increased taxonomic and biogeographic knowledge will stimulate interest among local researchers to conduct their own research on these fascinating aspects of weevil diversity.

Figure 8 .
Figure 8. Parallelodemas setifrons, dorsal view of head showing sexually dimorphic protrusion of eyes and rostral width (left male, right female).

.
The species is known only from China (Guizhou).The name is a participle presence active of dimeto (=to delimit, to mark-off; Latin).