Poteriophorus uhlemanni ( Schultze, 1922 )

Chamorro, M. Lourdes & Huang, Chia-Lung, 2019, Descriptions of the Immature Stages of Poteriophorus Schoenherr, 1838 (Coleoptera: Curculionidae: Dryophthorinae): Larva, Pupa, and Biology of Poteriophorus uhlemanni (Schultze, 1922) Discovered through Dawu Traditional Ecological Knowledge, The Coleopterists Bulletin 73 (2), pp. 283-299 : 288-296

Poteriophorus uhlemanni ( Schultze, 1922) Figs. 1–10

Description of Mature Larva. Habitus: Size range = 3‾ 28 mm (n = 33). Overall color creamy white; C-shaped, robust ( Fig. 4 ); abdomen ventrolaterally expanded from segment III–V then abruptly narrowed; cuticle smooth to finely asperate; cuticular spicules (asperities) distributed throughout. Head: Free, oval (in anterior view), surface medially and mesolaterally ridged ( Figs. 5E, G , 7A ); epicranial suture posteriorly prominent, raised; frontal suture incomplete, not extending to articulating membrane of mandibles; endocarinal line about 1/3 length of frons; frontoclypeal suture distinct; pseudoclypeus absent. Convergent, nonpigmented stripes visible anteriorly ( Fig. 5E ). Anterior stemmata present; posterior stemmata (according to May (1994), posterior stemmata visible in younger larvae) present besides des5 ( Fig. 7A, B ). Antenna ( Fig. 7C ) with a membranous, cushion-like, basal segment, an apical, convex sensorium, and a group of variously shaped sensillae; semi-cavernous. Hypopharyngeal bracon ( Fig. 7B ) without sclerome; postoccipital lamina (projection) present with apodemes; epicranium postocciput with hyaline, broadened posterior inflexion. Thorax: Thoracic terga without patches of spicules (asperities). Thoracic spiracle on prothorax, linear, orifice 3–4 times air tube length (elongate). Legs absent; pedal area distinct (bulging and setose). Abdomen: Dorsal abdominal superimposed lobes (I–VII) with 3 major lobes; setae absent between intersegmental fold (dorsal fold) and scutum; abdominal pleura subdivided into 2 or more superimposed lobes. Spiracles of segments I–VII prominent, spiracular air tubes well-developed, as long as orifice; direction of spiracular air tubes of abdominal segments I–VII dorsal; spiracles of abdominal segment VIII positioned on dorsal disc, air tubes directed caudad; segment VIII without lateral projections. Segments VIII and IX flattened dorsally. Posterior margin of abdominal segment IX without a pair of projections, broad and truncate. Segment X position ventral; shape of preanal lobe posteromedially deltoid, expanding anterolaterally; median lobe subrectangular; lateral anal lobes subdeltoid, membranous throughout.

Mouthparts. Clypeus on each side with 2 setae (cls1, 2) and 1 sensillum (clss). Labrum on each side with 3 setae (lms1–3): lms1 and lms3 hair-like, elongated, lms2 rod-like, half as long as lms1 and lms3 ( Figs. 9 , 10 ). Epipharynx trilobed medially ( Fig. 5H ); anterolateral epipharyngeal setae (als1–3) relatively long, tapering to apex; each side of anteromedian epipharyngeal margin with 2 setae (ams1, 2): ams1 short, rod-like, ams2 trifurcate (at least one) or bifurcate, median part of epipharyngeal margin with 3 setae (mes1–3), all short, not forked, mes1 and mes2 placed medially between labral rods, mes3 placed anteromedially, close to ams1 (see Discussion); sensory pores (snp) placed medially between (mes1 and mes2), posterior accessory sensory pores (pasps) located on labral rods; labral rods parallel-sided, distally widely joined (U-shaped); asperities short to moderately long, distinct, lateral to rods; medial asperities becoming moderately elongate medially, not anteriorly, forming a brush-like pubescent strip ( Fig. 8A ). Mandibles deltoid ( Fig. 5A–D ), approximately 1/3 length of head; mola absent, apical cutting edge absent, mandibular diagonal masticatory ridge absent; 1 internal-medial subapical projection; 1 marginal (dorsal/ventral; internal) subapical projection; single incisor cusps; 2 mandibular setae (mds1 and mds2) short, equal in length. Lateral lobes of hypopharynx (predominantly laterally) densely setose; terminating approximately at half length; chitinized arm of mentum 4 times longer than wide, angled and extending to hypopharynx. Maxillary stipes with 4 setae (sts 1–4 or if using different terminology 1 sts, 2 pfs, 1 mbs), lacinial lobe or spine absent, maxillary articulatory lobes absent; dorsal malar setae regularly aligned, singly, with 8 dorsal setae of mala (dms1–8), with increased branching proximally; dms (especially dms1–7) surrounded at base with asperities (short setae); 4–5 ventral malar setae (vms1–4 (5 )), vms1 and vms3 branched, vms2 unbranched, half or less than half length of vms1, vms4 contiguous, unbranched, greatly reduced (peg-like); vms5 seemingly absent; maxillary palp 2-segmented; second maxillary palpomere without accessory process, with group of peg-like sensilla arranged circularly ( Figs. 5F , 8C ). Labium ovoid, ligula with 2 setae lgs1 and lgs2 entire, variable in length; premental setae (prms) located medially (between forks of premental sclerite); postmental setae pms3 and pms2 situated laterally and pms1 located medially, distance among pms subequal; pigmentation of premental sclerite trident-shaped ( Fig. 8B ).

Chaetotaxy. Head with 5 dorso-epicranial setae (des1–5), all equal in length; des1–des3 placed mesally on epicranium, des3 above frontal suture, des5 antero-laterally; frons with 5 frontal setae (fs1–5): fs1 and fs2 minute, fs3 medium length, fs4 and fs5 elongated; fs1 placed close to frontal suture, fs2 medially, fs3 antero-medially, fs4 and fs5 anterolaterally; 4 posterior epicranial setae (pes1–5) in line above des1; 2 lateral setae (ls1 distinctly longer than ls2) and 2 ventral setae (ves1, 2) equal in size. Epicranial sensillum (es) not visible. Pronotum with 7 setae (prns1–7) ( Fig. 6A ) variable in length (3 elongated and 4 medium length); 2 pleural setae (ps1, 2) equal in length; mesonotum with 1 prodorsal seta (prs), 1 postdorsal seta (pds), 3 pairs of setae on alar area (as1–3) (1 long, 2 minute), single spiracular seta (ss), 2 epipleural setae (eps1, 2) variable in length, and 1 pleural seta (ps). Each pedal area with 5 setae of variable length. Chaetotaxy on metanotum as on mesonotum. Setae on abdominal segments I–VII short, fine; on segments VIII–IX long and coarse ( Fig. 6B ). Abdominal segments I–VII with 1 long prs, 4 pds (1 st prominent, next 3 minute), 1 ss of medium size, 1 pair of eps1, 2 of varible length, 1 ps of medium size, and 1 laterosternal seta (lsts). Abdominal segment VIII with 1 prs, 1 elongated pds (uncertain), 1 pair of elongated eps1, 2, 1 short ps, 1 short lsts. Abdominal segment IX with 1 long ds and 2 elongated ps. Each lateral anal lobe with a pair of minute terminal setae.

Description of Pupa. Male. Body length = 29–32 mm; body width = 12–16 mm (at widest point) (Fig. 16A–C). Widest at mesothoracic region. Vertex of head with subquadrate, dorsally flattened projections. Antennae laterad, emerging 1/4 from base of rostrum, size approximately as long as length of pronotum, slender, club clearly visible. Mandibular theca lacking setae. Metanotum approximately 2 times longer than mesanotum; meso- and metanotal widths subequal. Abdomen with 9 segments; pseudocerci on segment IX laterad, short, oblong, and truncate. Spiracles on abdominal segments I–VIII, anterolaterad.

Chaetotaxy. (Numbers indicated for one side only) Head: One vertical seta; 1 supraorbital seta; 1 orbital seta; 2 basirostral setae (1 large stout seta and 1 small seta basally) ( Fig. 9 ). Thorax: One apical pronotal seta; 2 lateral pronotal setae; 1 discal pronotal seta; 2 basal pronotal setae (1 minute); 3 mesonotal setae; 2 metanotal seta. Legs: Femoral seta presenta. Abdomen: Four postdorsal setae on segment I, 5 each on segments II–VI, 5 (4 closer together, projected) on segment VII, 4 (mesal 2 longer than lateral 2) on segment VIII, 3 (mesal 2 longer than lateral 3 rd) on segment IX. Last pair of legs largely exposed, not covered by pterothecae.

Comments. Adult males have a much longer and broader rostrum with copious ventral pubescence ( Figs. 2D , 3 ). Females have a rostrum approximately half to a third shorter than that of the male ( Figs. 2C , 3 ). Before immature stages were found, adults were rarely captured and observed in the field.

Bionomics. Calamus siphonospathus ( Fig. 1A ) is the only known host plant for larvae. The larva tunnels in the palm frond. Upon discovery of the host plant, adults became more easily encountered under the forest canopy, flying high above the ground. The behavior of the female was observed as follows. They chew a small hole and lay into it a single egg. When the first instar hatches, it drills into the leaf-sheath and causes a dark brown mark on the surface. The larva feeds on the inner part of the leafsheath and forms a straight or irregular feeding tunnel. More than one larva was found within one meter of the stem, but the feeding tunnels did not meet. The mature larva makes a chamber or cocoon of feeding residue (frass and sawdust) and fibers in the tunnel before pupation ( Fig. 2A ). After emerging from the pupa, the adult remains in the chamber and does not immediately emerge from the tunnel. The species is multivoltine, and the generations are overlapping. Newly emerged adults and young and mature larvae are often within the same stem (based on field collecting in May 2014 and August 2015) ( Figs. 1D–E , 3 ).

Distribution. This species is found in Taiwan, only on the eastern offshore island of Lanyu, and the Philippines ( Fig. 10 ).

Diagnosis. The larva of Poteriophorus resembles that of Metamasius Horn , Sphenophorus , Rhabdoscelus , Trochorhopalus , and most other Sphenophorina based on the following characters: epipharynx with three anterolateral setae, entire (not tuft-like or branched); epipharyngeal sensory pores present; mala with eight dorsal malar setae, tuft-like; dorsal surface of mala with elongate asperites among setae; mala with 4–5 ventral malar setae (3–5 for subtribe); labral seta bifurcate; thoracic spiracle 3–4 times longer than wide; posterior margin of abdominal segment IX entire, not produced into digitate processes and with four pairs of discernible setae.

Larvae of Poteriorphorus can be distinguished from the most commonly encountered larvae of Metamasius and Sphenophorus by the following characters (based on currently known forms): (1) Poteriophorus has an elongate head and ridged frons, Sphenophorus and Metamasius have a circular head and a smooth frons; (2) epipharynx of Poteriophorus with medial epipharyngeal setae (mes3) located distally and subapically and two pairs of anteromedial setae (ams1, 2) discernible, whereas Sphenophorus (character shared with Metamasius ) appears to have three pairs of anteromedial setae (one pair is interpreted as mes3), located linearly on the apex, with at least two pairs branched; (3) Poteriophorus has tuft-like malar dorsal setae, similar to Sphenophorus and Metamasius , but in Poteriophorus the setae branch distally, especially the basal (proximal) dorsal malar setae, in Sphenophorus and Metamasius the setae branch medially, at least; (4) Poteriophorus has a single labral basal sensillum, as in Metamasius ; Sphenophorus usually has two; (5) Poteriophorus bears asperites on the hypopharynx (as in Sphenophorus ) and lacks pubescence (asperites) on the ligula (most Sphenophorus ), unlike Metamasius , which has asperites on the ligula; (6) epipharyngeal lateral and medial surfaces are each covered with asperites in Poteriophorus (and Sphenophorus ), but are discretely positioned laterad on both the medial and lateral surfaces in Metamasius ; (7) Poteriophorus has a single labral pore as in Metamasius , two labral pores in most Sphenophorus . For a more comprehensive identification resource to all currently known dryophthorine genera, consult Chamorro (2019).

Material Examined/Measured. Poteriophorus uhlemanni : TAIWAN: Kotosho [Lanyu], (22°3 ′ 4″ N, 121°32 ′ 27″ E) , viii.1935, coll. T. Takaki ( TARI), USNMENT01119814 , Ƌ, ♀; Taitung County, Lanyu , (22°3 ′ 4″ N, 121°32 ′ 27″ E) , Jan. 2014, from Calamus siphonospathus (Arecaceae) , coll. Dawu local ( USNM), det. Chamorro, M.L., USN- MENT01119878, 1 larva [dissected], 23.5 mm; USNMENT01070985, 1 larva [dissected], 18 mm; USNMENT01448597, 12 larvae, 9, 10, 12, 15, 15, 17, 17, 18.5, 21, 21.5, 23, and 25 mm ( USNM, NTNU, ANIC) ; Feb. 2014, USNMENT01119879, 1 larva [dissected], 26 mm; USNMENT01448598, 7 larvae, 12, 17, 19, 19, 20, 22, and 23 mm ( USNM) ; March 2014, USNMENT01119876, 1 pupa, Ƌ, 32 mm; USNMENT01119870, 1 prepupa, 28 mm; April 2014, USNMENT01448599, 5 larvae, 3, 10, 17, 18, and 19 mm, 1 headless pupa, 29 mm; USNMENT01448001, 1 larva [dissected], 23 mm, ( NTNU) ; May 2014, USNMENT01119985, Ƌ, 28.5 mm; USNMENT01119986, 1 larva [dissected], 25 mm; USNMENT01119871, 4 larvae, 18.5, 20, 21.5, and 22 mm; 21.vii.2016, USN- MENT01119984, Ƌ, coll. Local collector ( USNM) . PHILIPPINES: Eastern Luzon, Quirino, Maddela, Disimungal , Sierra Madre , [16.342747° N, 121.905563° E] , September 2015, local collector, USNMENT01119875, Ƌ ( USNM) .

Material Examined of Other Dryophthorinae. USNM slide collection: Sphenophorus pertinax (Olivier) : Leng 336, R.T. Cotton; Sphenophorus robustus Horn : USA: Calif. R.T. Cotton; Sphenophorus pontederiae Chittenden : Mass, Stoughton, in rootstocks Pontederia cordata, Aug. 1924 , D.H. Blake coll.; Sphenophorus maidis Chittenden : South Carolina, Lee Co., Meredith, O. L. Cartwright; Metamasius hemipterus sericeus (Olivier) : MEXICO: Veracruz, R. T. Cotton; Metamasius ritchiei Marshall , JAMAICA: Kingston, Sept. 16, 1917, A. H. Ritchie.

Figures

Fig. 1. Habitat and specimens of Poteriophorus uhlemanni. A) Habitat and host plant, Calamus siphonospathus, in Lanyu, B) Collected specimens segregated by month, C) Development site of Poteriophorus, D) Leaf sheath removed to show the feeding tunnel and posterior part of the younger larva, E) Adult emerging from feeding tunnel.

Fig. 2. Tunnel, larva, and adult of Poteriophorus uhlemanni. A) Larval tunnel sealed with frass and sawdust, B) Leaf sheath removed to show dorsal view of larva in the feeding tunnel, C) Female with sexually dimorphic shorter, non-pubescent rostrum, D) Male with sexually dimorphic large, ventrally pubescent rostrum, length = 28.5 mm (USNMENT01119985).

Fig. 3. Artistic rendition of the life history of Poteriophorus uhlemanni, depicting egg, larvae (not all instars shown), pupa, frass and sawdust cocoon, newly eclosed adult in host plant tunnel, male (above), female (below), and human hand alluding to the Dawu Traditional Ecological Knowledge that led to discovery of the immatures and host plant. Hand and beetles are to scale. Illustration by Joel Floyd.

Fig. 4. Mature larva of Poteriophorus uhlemanni. A) Lateral view with inset of thoracic spiracle (USNMENT01119871), B) Ventral view (USNMENT01119871), C) Caudal view, showing abdominal segments VII–IX and spiracles on segments VII and VIII (USNMENT01119871), D) Lateral view of abdominal segments V–VIII and respective spiracles (USNMENT01119870).

Fig. 5. Larval mouthparts and head of Poteriophorus uhlemanni. Left mandible (USNMENT01119878): A) Ventral view, B) Mesoventral view, C) Mesodorsal view, D) Dorsal view. E) Head with right mandible attached, dorsal view (USNMENT01119879), F) Maxillary-hypopharyngeal complex, ventral view (USNMENT01070986), G) Head with right mandible attached, lateral view (USNMENT01119879), H) Epipharynx, ventral view (USNMENT01119879).

Fig. 6. Larva of Poteriophorus uhlemanni (USNMENT01119871), lateral views of A) Head and thorax, B) Abdomen. Abd I = abdominal segment I; as = alar seta; dpls = dorsopleural seta; ds = dorsal epicranial seta; ls = lateral seta; pds = postdorsal seta; prns = pronotal seta; prs = prodorsal seta; ps = pleural seta; ss = spiracular seta; sts = sternal seta; Th I–III = thoracic segments I–III; vpls = ventropleural seta.

Fig. 7. Larval head of Poteriophorus uhlemanni. A) Head capsule, anterior view. cls = clypeal seta; des = dorsal epicranial seta; fs = frontal seta; pes = posterior epicranial seta (USNMENT01119879), B) Head capsule, posterior view (USNMENT01119878), C) Antenna, oblique lateral (left) and anterior (right) views (USNMENT01119878).

Fig. 8. Mouthparts of Poteriophorus uhlemanni. A) epipharynx. als = anterolateral epipharyngeal seta; ams = anteromedian epipharyngeal seta; mes = medial epipharyngeal seta; pasps = posterior accessory sensory pores; snp = sensory pores (USNMENT01119878), B) Labium, posterior view. lgs = ligular seta; pms = postmental seta; prms = premental seta (USNMENT01119879), C) Maxillae, dorsal (anterior) view. dms = dorsal malar setae (USNMENT01119878), D) Labrum, anterior view. lms = labral seta (USNMENT01119878).

Fig. 9. Male pupa of Poteriophorus uhlemanni, terminology follows May (1994) and Oberprieler et al. (2014) (USNMENT01119876). A) Lateral view, facing dorsally, B) Dorsal view, C) Ventral view. Darkening of specimen in photograph is a possible result of the method of preservation.

Fig. 10. Distribution of Poteriophorus uhlemanni. A) Taiwan and Philippines, B) Taiwan and island of Lanyu.