Metapocyrtus (Orthocyrtus) hirakui, Cabras & Medina & Bollino, 2021

Cabras, Analyn A., Medina, Milton Norman & Bollino, Maurizio, 2021, Two new species of the genus Metapocyrtus Heller, 1912 (Coleoptera, Curculionidae, Entiminae, Pachyrhynchini), subgenus Orthocyrtus Heller, 1912, from Mindanao Island, Philippines, ZooKeys 1029, pp. 139-154 : 139

Metapocyrtus (Orthocyrtus) hirakui sp. nov. Figs 5 , 6

Holotype

(Fig. 1A, B ), male: Philippines - Mindanao / Bukidnon / Lantapan / July 2018 / coll. Medina (typed on white card) // HOLOTYPE male / Metapocyrtus (Orthocyrtus) hirakui / CABRAS, MEDINA & BOLLINO, 2021 (typed on red card) Presently in UMCRC, it will be deposited in Philippine National Museum of Natural History (PNMNH) under the National Museum of the Philippines (NMP).

Paratypes.

28♂♂, 39 ♀♀: 3♂♂, 15 ♀♀, Philippines - Mindanao/ Bukidnon / Lantapan / V-VII.2018 / coll. Medina; 7♂♂, 4 ♀♀, Philippines - Mindanao/ Bukidnon/ Talakag/ VII. 2018/ Leg, L.C. All in UMCRC; 7♂♂, 2♀♀: Philippines - Mindanao / Cabanglasan - Bukidnon / III-IV.2013 / m. 800-1000 - Leg. Loc. people / coll. M. Bollino; 7♂♂, 14♀♀: Philippines - Mindanao / Cabanglasan (Bukidnon) / September 2013 / ex. N. Mohagan / Lg. local people - coll. Bollino; 1♂, 1♀: Philippines - Mindanao / Cabanglasan / (Bukidnon) / December 2018 - January 2019 / Lgt. local people - coll. Bollino; 1♂: Philippines - Mindanao / Kalatungan / (Bukidnon) / X.2015 / ex I.Lumawig - coll. Bollino; 2♂♂, 3 ♀♀: Philippines - Mindanao / San Fernando - Bukidnon / X.2013 / ex Lumawig / lg. Local people - coll. Bollino, all in MBLI. All paratypes with additional red label: PARATYPE / Metapocyrtus (Orthocyrtus) hirakui / CABRAS, MEDINA & BOLLINO, 2021

Diagnosis.

Metapocyrtus (Orthocyrtus) hirakui sp. nov. differs from all other species of the subgenus for its unique elytral ornamentation consisting of yellow ochre to blue longitudinal stripes and striae I to II occasionally interrupted in the middle, although generally such striae are continuous from the base to the apex of elytra.

Description.

Male. Dimensions (in mm): LB 10.6-10.9 (holotype 10.9, â: 10.75). LR: 1.9-2.0 (holotype 2.0, â: 1.95), WR 1.3-1.5 (holotype 1.5, â: 1.4), LP: 3.0-3.1 (holotype 3.0, â: 3.05), WP 3.0-3.1 (holotype 3.0, â: 3.05), LE: 6.9-7.0 (holotype 6.9, â: 6.95), WE: 4.9-5.0 (holotype 5.0, â: 4.95). N = 4.

Integument black. Body surface, rostrum, head, and underside subopaque.

Body subglabrous. Head subglabrous, sparsely, minutely pubescent, with light-yellow ochre, round scales interspersed with metallic-white, hair-like, elliptical scales on lateroventral parts; forehead between eyes partially covered with metallic, light-yellow ochre, round scales; median groove barely distinct, not reaching the vertex. Rostrum sparsely, minutely pubescent, slightly longer than wide (LR/WR: 1.33), dorsum faintly, minutely punctured, bearing minute, yellowish hairs, white, recumbent, hairlike scales on the lateral surface, and long, light-brown hairs at the anterolateral margin; transverse basal groove distinct; basal half with shallow depression covered with metallic yellow ochre, round and elliptical scales; lateroventral part behind antennal scrobe densely covered with round to elliptical, white and yellow ochre scales, sparsely interspersed with short, hair-like white scales; dorsal surface weakly convex. Eyes medium-sized and feebly convex. Antenna moderately clavate, scape slightly shorter than funicle, moderately covered with fine, light-colored hairs. Funicular segments I and II almost of the same length, nearly three times longer than wide; segments III-VII slightly longer than wide; club subovoid, nearly three times longer than wide. Prothorax subglobular, as long as wide (LP/WP 1.0), faintly punctured with sparse minute hairs, widest at middle, weakly convex, with a faint groove along midline reaching the middle, and with the following scaly markings of metallic light yellow ochre, and shagreen, round scales: a) thin band at the anterior margin, b) transverse band in the entire width in middle, and c) lateroventral stripe before the coxa confluent with the anterior margin and transverse band at middle. Elytra short ovate (LE/WE 1.38), wider and longer than prothorax (WE/WP 1.67, LE/LP 2.3), black, subglabrous, strongly convex with very minute and sparse setiferous punctures, each puncture with light-colored, short seta. Elytra with scaly bands of metallic light-yellow ochre, turquoise, and blue, round scales covering stria I-IX, beginning shortly from anterior margin and extending towards apex, sometimes stria I and II interrupted at middle creating a subcircular, broad, glossy black spot without scales. Stria I-IX confluent at anterior margin; stria I, II, III, VIII, and IX confluent at the apex. Stria IV and V confluent at apical quarter. Apex with light-colored hair. Legs with moderately clavate femora. Femora covered with light-colored hair and sparse, pale-blue elliptical, hair-like scales towards apical part. Tibiae covered with subrecumbent, light-colored bristles, and weakly serrate along inner edge. Fore and mid tibiae bear a mucro at apex, and hind tibiae with apical mucrones vestigial. Tarsomeres covered with sparse pubescence. Procoxae with light-colored hair covered with pale green and light yellow-ochre round to elliptic scales on the anterior side interspersed with white hair-like scales. Mesocoxae and metacoxae with light-green hairs and sparsely covered on the anterior side with pale-blue, hairlike, round scales, less dense on metacoxae. Mesosternum covered with light-colored, adpressed bristles. Metasternum with light-colored, adpressed bristles and sparse, light-yellow ochre, round scales at lateral sides. Ventrite 1 depressed on disc with light-colored, adpressed bristles and sparse, light-yellow ochre, round scales towards lateral margin interspersed with white, hair-like scales. Ventrite 2 with long, light-brown, adpressed bristles, shorter towards margin. Ventrites 3-5 with sparse, light-colored, short bristles. Ventrite 5 flattened, apical half finely densely punctured.

Male genitalia as shown in Figure 2A-C .

Endophallus as shown in Figure 3 . Cabras, Bollino and Medina (2018) noted that obtaining the complete eversion of the endophallus in the subgenus Metapocyrtus Orthocyrtus is particularly complicated due to the long flagellar diverticulum, and attempts are very often subject to partial failure because the flagellar diverticulum itself tends to remain invaginated. Long series of males are needed to obtain a complete or even a partial but acceptable evertion, as it was in this case (18 males available, no full, nine partial, but only five acceptable partial evertions obtained).

Even if the number of completely everted endophalluses belonging to taxa of the subgenus Metapocyrtus Orthocyrtus is still very few, it is possible to try to hypothesize the taxonomic value of this genitalic structure. From what we have observed, the flagellar diverticulum does not seem to have a species-specific morphology and is quite uniform both in shape and in length, in contrast, for example, to the subgenus Artapocyrtus Artapocyrtus (Bollino, Sandel & Yoshitake, 2019). What appears to have significant taxonomic value is the shape and presence/absence of the basal, baso-lateral, and median diverticula. In studying Orthocyrtus , the rate of acceptable eversion of the endophallus is about 30% of the samples tested, and although it is possible to obtain a complete evertion in approximately 1% of the samples, it will still take a long time before we can reach conclusions that are not just working hypotheses.

Female. Dimensions (in mm): LB 12.0-13.8 ( â: 12.66), LR 2.0-2.2 ( â: 2.12), WR 1.4-2.0 ( â: 1.57), LP 3.2-3.8 ( â: 3.56), WP 3.2-3.8 ( â: 3.51), LE 8.9-10.0 ( â: 9.14), WE 5.5-6.8 ( â: 5.86). N = 15.

Habitus as shown in Figure 1D-F .

Females differ from males by the following: a) head and rostrum mostly glabrous with only a few, sparse, yellow ochre, round scales and blue, hair-like scales on lateral and latero-ventral sides, b) pronotum slightly longer than wide in female (LP/WP 1.0), c) pronotum subglobular; thin, transverse, median band interrupted at middle, d) elytra subovate (LE/WE 1.47-1.62), slightly longer and wider (WE/WP 1.72-1.79, LE/LP 2.63-2.78) than male; stria I and II interruption at middle creating a subcircular, broad, glossy black spot without scales; e) ventrite 1 flattened or slightly convex on disc. Otherwise, femail similar to the male.

Etymology.

The specific epithet is named after Hiraku Yoshitake (Tsukuba, Japan) for his great contribution in the advancement of studies on Pachyrhynchini in the Philippines.

Distribution.

Metapocyrtus (Orthocyrtus) hirakui sp. nov. is known so far only from the province of Bukidnon.

Brief ecological notes

Specimens of M. (O.) davaoensis sp.nov. were collected on leaves of Swietenia macrophylla King ( Meliaceae ) at the ridge near Tamugan river in Calinan (Western part of Davao City) with an estimated altitude of 800 m (Fig. 5A ). The biotope is a mix of secondary and agroforest. Barangay Calinan is characterized by rugged terrain and adjacent to several mountain ecosystems such as Mt. Carmen and Mt. Tamayong, with considerably higher elevation compared to the downtown area of Davao City. The river near where the new species was collected is quite pristine as evidenced by the presence of Odonates inhabiting only pristine fluvial systems such as Eupheae amphicyana Ris, 1930 and Neurobasis anumariae Hämäläinen, 1989. This biotope also has lush vegetation with several plants such as Medinilla sp. ( Melastomataceae ), Ficus spp. ( Moraceae ), Cyathea sp. ( Cyatheaceae ), and Bambusa spp. ( Poaceae ), among others. Despite the conversion of surrounding areas to maize and banana farms, it is still rich with Pachyrhynchini weevils particularly members of the genus Metapocyrtus . Some of the Metapocyrtus species documented within a radius of 500 meters from the banks of the river are Metapocyrtus (Dolichocephalocyrtus) lineaticollis Schultze, 1925, M. (Dolichocephalocyrtus) bituberosus Heller, 1912, M. (Trachycyrtus) apoensis Schultze, 1925 and M. (Trachycyrtus) adspersus Waterhouse, 1843. Compared with the aforementioned Metapocyrtus species which are abundant in the area, the new species is quite rare with only a few individuals documented. No species of Pachyrhynchus were observed. Moreover, the discovery of this new species within the remaining green spaces of Davao City reiterates the importance of our urban green spaces as a remaining haven for different species of flora and fauna and calls for immediate conservation measures.

Metapocyrtus (Orthocyrtus) hirakui sp.nov., on the contrary, was abundant in a secondary forest with some old growth trees near Lantapan, with an elevation of approximately 1200 m (Fig. 5B ) The new species was present all over the area and collected on several plants, namely Bridelia sp. ( Phyllanthaceae ), Oleandra sp. ( Oleandraceae ), Clerodendrum sp. ( Lamiaceae ), Ageratum conyzoides ( Asteraceae ), Camellia sp. ( Theaceae ), Medinilla sp. ( Melastomataceae ) and Nephrolepis sp. ( Nephrolepidaceae ). However, they were more abundant along trails and open areas. As documented previously, the majority of the Pachyrhynchini including Metapocyrtus are often collected along trails and ridges which are either fully or partially exposed to the sun ( Cabras et al. 2019). The interior of the forest does not usually give an outstanding result in terms of collecting Pachyrhynchini .

Notes on mimicry

Mimicry is well investigated in butterflies but far less understood in beetles which possess equally interesting mimetic patterns ( Meyer 2006). The first record of mimicry among Pachyrhynchini was noted by Wallace (1889), who noticed sympatric species sharing the same integument colours and elytral patterns. This was also noted by Schultze (1923, 1925), who provided a list of 19 sympatric species of Pachyrhynchus , Metapocyrtus , and Doliops sharing the same coloration and patterns. He also reported 14 sympatric species of Metapocyrtus , exhibiting very similar elytral patterns, which were only separable after a closer inspection of diagnostic characters such as the rostrum ( Schultze 1925). A study by Tseng et al. (2014) found that the diverse mimicry of Pachyrhynchini weevils are taking advantage of their coloration as aposematic signals in deterring predators, exploiting predators’ visual system. Pachyrhynchini do not possess toxins as in butterflies, but they do have a very hard elytra, which deter predators and act as a secondary defense of an aposematic insect ( Schultze 1923; Wang et al. 2018). As mentioned by de Jager and Anderson (2019), mimicry can be confirmed using three conditions, namely "(1) characterizing a model, (2) identifying a receiver with a percept of said model, and (3) demonstrating that the receiver exerts selection on the mimic". This sympatric and allopatric convergence of colors and patterns has been greatly observed among Pachyrhynchini and other Entiminae weevil groups such as Alcidodes , Polycatus , Eupyrgops , Neopyrgops , Coptorhynchus , and the long-horned beetle Doliops , which can be an outstanding example of the mimetic complex. This occurrence has also been observed among spiders, and other insects of the orders Heteroptera and Orthoptera , which show superficial resemblance and body coloration and pattern ( Wallace 1889; Cabras et al. unpublished).

Metapocyrtus (Orthocyrtus) davaoensis sp. nov. was collected at nearly the same locality as M. kitangladensis Cabras, Medina & Zhang, 2019. This suggests a possible mimicry between these two species, for they have similar elytral markings. Photographic documentation suggests the presence of M. (O.) davaoensis sp. nov. in Marilog District, Davao City, where M. kitangladensis Cabras, Medina & Zhang, 2019 was also documented. The importance of the geographic distribution of the model as the limiting factor for the effectiveness of the mimicry complex has already been established. As Ries and Mullen (2008) mentioned "the advantage of mimicry does not extend beyond the range of the model", although allopatric convergence of colors has also been documented.

Metapocyrtus (Orthocyrtus) hirakui sp. nov. belongs to a mimetic complex involving Pachyrhynchus tikoi Rukmane, 2016, Doliops valainisi Barsevskis, 2013, and Polycatus mimicus Bramanti, Bramanti, & Rukmane, 2020, with all species sharing a superficial resemblance. These four species were collected in an area of less than 500 m diameter and at times from the same plant. Metapocyrtus (O.) hirakui and P. tikoi were very abundant in the secondary forest of Lantapan, Bukidnon, and could be easily interchanged due to their uncanny resemblance. Some Polycatus species have previously been recorded to possibly be part of the Pachyrhynchini mimicry complex. Sometimes they exhibit a perfect mimicry, looking exactly like some Pachyrhynchini models, while at other times they exhibit imperfect mimicry and do not have exactly the same pattern. According to Forsman and Appelqvist (1998), even only the superficial resemblance and coloration of the elytra of imperfect mimicry is enough to fool visual predators which mostly rely on patterns and coloration in their choice of prey. Polycatus can be easily distinguished from Pachyrhynchini by the rostrum which is entirely continuous with the head, the complete metepisternal suture, the distinct squamose scutellum, the definite epistome on the rostrum, and the antenna club which has the first joint much longer than the rest, together with its basal half narrowed into a conspicuous peduncle. As expected in this case of Batesian mimicry, mimics ( Polycatus mimicus and Doliops valainisi ) were much less numerous in the field than models ( Metapocyrtus (Orthocyrtus) hirakui sp. nov. and Pachyrhynchus tikoi Rukmane 2016).

Figures

Figure 1. Metapocyrtus (Orthocyrtus) davaoensis sp. nov. A male holotype, dorsal view B female, dorsal view C ditto, male, lateral view D ditto, female, lateral view.

Figure 2. Metapocyrtus (Orthocyrtus) hirakui sp. nov. A male holotype, dorsal view B female, dorsal view C ditto, male, lateral view D ditto, female, lateral view.

Figure 3. Metapocyrtus (Orthocyrtus) hirakui sp. nov. everted endophallus, lateral view.

Figure 5. Habitat of Orthocyrtus spp. A O. davaoensis sp. nov in Davao City B O. hirakui sp. nov. in Lantapan, Bukidnon.

Figures 6. Mimicry of Metapocyrtus (Orthocyrtus) davaoensis sp. nov. and Metapocyrtus (Orthocyrtus) hirakui sp. nov. A M. (O.) davaoensis sp. nov. B Metapocyrtus kitangladensis C Pachyrhynchus tikoi D M. (O.) hirakui sp. nov. E Polycatus mimicus.