Proterhinus tauai Brown, 2019

Brown, Samuel D. J., 2019, A new species of Proterhinus Sharp, 1878 (Coleoptera: Curculionoidea: Belidae) from Miti‘aro, Cook Islands, South Pacific, Zootaxa 4664 (4), pp. 481-496 : 483-488

Proterhinus tauai Brown , new species

http://zoobank.org/ urn:lsid:zoobank.org:act:A648AAF8-FB12-41BF-B800-3CE1AEFDD10F

Figures 2, 3, 4, 5 , 6, 7 , 8, 9 , 10, 11, 12, 13, 14, 15, 16, 17, 18

Diagnosis. Dorsum covered with decumbent to suberect brown clavate scales ( Figures 2, 3 ); lacking long setae on lateral regions of elytra. Antennae short, not reaching posterior margin of pronotum when directed backwards ( Figures 4, 5 ). Pronotum with lateral margins subparallel, anterior angles produced anteriorly.

Description. Body length 1.52 mm to 2.53 mm (= 2.02 mm, s = 0.25, n = 33), height 0.44 mm to 0.70 mm (= 0.57 mm, s = 0.07, n = 33). Integument black; sometimes with diffuse dark red to strong red maculae on the lateral regions of the elytra, occasionally extending onto the pronotum. Dorsum covered with decumbent to suberect light greyish yellowish brown clavate scales, variably condensed into maculae ( Figures 2, 3 ). Mouthparts. Females with mandibles subtriangular, left overlapping the right; prementum subquadrate. Males with mandibles large, fal- ciform, laterally with fine setae; prementum large, triangular. Rostrum. Females with narrower, subrectangular rostrum in dorsal view ( Figure 6 ); widest immediately in front of eyes, gently tapering towards apex; multicarinate, dorsum with five low blunt carinae which are devoid of scales; ventrolateral margin with multiple erect setae; un- derside with inconspicuous fine setae, appears nude; length 0.37 mm to 0.52 mm (= 0.44 mm, s = 0.05, n = 12), distal width ( Figure 8 ,) 0.25 mm to 0.31 mm (= 0.28 mm, s = 0.02, n = 12), length/width ratio 1.42 to 1.74 (= 1.61, s = 0.10, n = 12). Males with broad semicircular rostrum in dorsal view; widest approximately one eye diameter in front of eyes, sharply constricted between this point and eyes ( Figure 7 ); underside with sparse, fine setae. Length 0.23 mm to 0.49 mm (= 0.36 mm, s = 0.07, n = 21), distal width ( Figure 9 ,) 0.37 mm to 0.84 mm (= 0.59 mm, s = 0.14, n = 21), length/width ratio 0.56 to 0.69 (= 0.61, s = 0.04, n = 21). Antennae. At full length reaching about midpoint of pronotum. Segment 1 pyriform, as long as segment 2 + 1/2 segment 3, inserted ventrally. Segment 2 pyriform, as long as segment 3 + 1/4 segment 4, about as wide as segment 1. Segments 3–6 pyriform, subequal in length and width, about 1/2 width of segment 2. Segments 7–11 getting progressively longer and wider, with segments 9–11 forming a loose club. Head. Eye hemispherical, strongly protuberant; coarsely faceted; interocular scales present. Males with underside having large scattered punctures. Females with underside unpunctured. Pronotum. Length 0.43 mm to 0.72 mm (= 0.57 mm, s = 0.08, n = 33), width 0.53 mm to 0.89 mm (= 0.71 mm, s = 0.10, n = 33), length/width ratio 0.73 to 0.90 (= 0.81, s = 0.04, n = 33). Anterior angles produced anteriorly in both sexes. Lateral margins subparallel. Disc strongly punctured. Surface matte, without distinct microsculpture. Elytra. Length 0.93 mm to 1.67 mm (= 1.26 mm, s = 0.17, n = 33), width 0.65 mm to 1.07 mm (= 0.86 mm, s = 0.11, n = 33), length/width ratio 1.31 to 1.61 (= 1.47, s = 0.07, n = 33). Striae confused, not forming clear rows, coarsely punctured. Surface matte, without distinct microsculpture. Thoracic ventrites. Anterior end of metanepisterna reduced, not protruding into lateral elytral margin. Metaventrite coarsely punctured, vestiture sparse and fine. Abdomen. Ventrites impunctate, clothed with short, fine, inconspicuous setae. Legs. Femora stout, maximum girth in distal 1/3; scales more numerous apicad of widest point. Tibiae subcylindrical; setae on dorsal margin short, inconspicuous. Tarsi pseudotrimerous; segment 1 short; segment 2 bilobed, about 3 times as long as segment 1, clothed underneath with dense setae, lobes normally developed and symmetrical on all legs in both sexes; segment 3 concealed; segment 4 about as long as rest of tarsal segments combined; claws large, divergent. Male genitalia. Figures 10–13 . Tergite 8 concealed, retractable under tergite 7, posterior margin entire; rectal loop open anteriorly. Sternite 8 largely membranous, lightly sclerotised. Sternite 9 asymmetrical; spiculum gastrale short, barely as long as longest lateral arm of the sternite. Tegmen with parameral sector broadly rounded, bearing scattered setae. Pedon longer than tectum; pedon narrowly rounded at apex, tectum broadly rounded, nearly truncate. Female genitalia. Figures 14–18 . Tergite 8 with 4 teeth on posterior margin; rectal loop open anteriorly. Sternite 8 a lightly sclerotised loop with small setae on the posterior margin. Gonocoxites narrow, about 3.5 times longer than wide; styli absent.

Type material examined: Holotype. Male ( NZAC). Specimen mounted on card triangle; abdomen removed, dissected and mounted in DMHF on white card below specimen. Labelled ‘ COOK ISLANDS / Airport, Kaapoto / Mitiaro / 17 March 2017 / SDJ Brown’ [printed, off-white card], ‘ Beaten from Suriana / maritima / 19.8401°S 157.7094°W’ [printed, off-white card], ‘ HOLOTYPE / Proterhinus / tauai / Brown 2018’ [printed, red card].

Paratypes. A total of 32 specimens (20 males, 12 females) designated as paratypes, bearing blue paratype label. Paratype specimens deposited in NZAC, ANIC, BPBM, CMNC, NHM, USNM.

Miti‘aro: Airport, Kaapoto , 17 Mar 2017, SDJ Brown , beaten from Suriana maritima , 19.8401°S 157.7094°W (BPBM: 1, NZAC: 1); Villages, 17 Mar 2017, SDJ Brown , beaten from dying coconut frond, 19.8601°S 157.7196°W (NHM: 1); Vaikoua, 18 Mar 2017, SDJ Brown , beaten from Chamaesyce fosbergii , 19.8453°S 157.7179°W (NZAC: 1). Vainano, 18 Mar 2017, SDJ Brown , beaten from Suriana maritima , 19.8406°S 157.7131°W (BPBM: 1, CMNC: 1, NHM: 1, NZAC: 4, USNM: 1); Te Unu, 22 Mar 2017, SDJ Brown , beaten from Chamaesyce fosbergii , 19.8882°S 157.6912°W (ANIC: 1, BPBM: 1, NHM: 2, NZAC: 4, USNM: 1); Oavea, 22 Mar 2017, SDJ Brown , beaten from Chamaesyce fosbergii , 19.8960°S 157.7108°W (CMNC: 1, NZAC: 6); Northeast coast, 23 Mar 2017, SDJ Brown , beaten from Suriana maritima and Cassytha tangle, 19.8498°S 157.6828°W (ANIC: 1, BPBM: 1, NZAC: 3);

Distribution. This species is known only from Miti‘aro, Cook Islands, South Pacific ( Figure 1 ).

Biology: Specimens were collected from coastal scrub ( Figure 19 ), especially from Suriana maritima and Chamaesyce fosbergii (Sherff) Croizat & O.Deg (Euphorbiaceae) which were entwined with the parasitic vine Cassytha filiformis ( Figure 20 ). All specimens were collected by beating vegetation over a fabric tray.

Remarks. Proterhinus tauai is closely related to P. brevicornis Zimmerman and Perrault, 1989 , as evidenced by the similarities between the two species in the form of the dorsal vestiture, shortened antennae and the shape of the rostrum in both sexes. It differs from P. brevicornis by having the anterior angles of the pronotum produced anteriorly and ventrite 1 being impunctate.

It is also similar to P. phoenix , with both species having similar dorsal vestiture, and being similarly found on a low relief island. However, P. tauai differs from P. phoenix by having the anterior angles of the pronotum produced anteriorly and the dorsal surfaces more coarsely punctured. The males of P. phoenix also have a remarkably long spine on the ventral surface of all tarsal segments 1, which is not present in P. tauai .

Although superficially similar in facies to species of Aralius , especially A. wollastoni (Sharp) from New Zealand, P. tauai can be readily placed in Proterhinus by the following characters which distinguish the two genera ( Kuschel 2003): antennal segments 1 are longer than segments 2, ventrites 1–4 are smooth, without grooves or impressions laterally; males do not have a setiferous pit behind the postmentum; and females have only four teeth on the apical margin of tergite 8.

This species was not found on ‘Atiu, Mangaia or Rarotonga, despite searches by the author in similar habitats to those in which it had been found on Miti‘aro.

Etymology. Named after Taua, first missionary on Miti‘aro. Originally from Taha‘a in the Society Islands, he arrived on Miti‘aro in 1823 through the agency of the London Missionary Society ( Williams 1837, Lange 2005). He faithfully served on Miti‘aro for 18 years before returning with his family to Taha‘a.

Behavioural observations. Unfortunately, captive rearing offered few insights into the behaviour and biology of P. tauai . Specimens observed during the day were found deep in the leaf clusters of S. maritima or on the stems of C. filiformis . No unequivocal feeding damage was seen, though some oval abrasions were observed on the leaves of S. maritima and on the stems of C. filiformis . One possible oviposition hole was observed in the node where C. filiformis was parasitising S. maritima . The weevils were generally lethargic, with little movement occurring during observation periods. No inter-individual interactions were observed.

Rostrum allometric relationships. Rostrum traits varied between males and females in three of the four traits investigated. The distal width of the rostrum presented the greatest disparity between the two sexes. Males had a positively allometric relationship (b male = 1.739) between distal width and body length, while the same trait in females was negatively allometric (b female = 0.675) ( Figure 21 ; Table 1 ). Basal width and rostrum area showed similar patterns of being positively allometric in males (b male = 1.566 and b male = 1.745 respectively), and negatively allo- metric in females (b female = 0.702 and b female = 0.858 respectively). Rostrum length was the exception where sex did not significantly improve the model. This trait was positively allometric for both sexes (b = 1.438).

In contrast, none of the models fitted for the non-rostral traits showed significant differences between the sexes, resulting in a single line being fitted for these traits ( Table 1 ). Pronotum width ( Figure 22 ) was isometric (b = 1.036), while elytral width and body height were both slightly negatively allometric (b = 0.9).

Comparing the distributions of male rostrum distal width, female pronotum width and female elytral width, shows some overlap between the first two traits ( Figure 23 ), but minimal overlap between male rostrum distal width and female elytral width ( Figure 23 ). A total of 43% of males had rostral widths that were greater than the female with the narrowest pronotum, while 75% of females had pronotal widths that were less than the widest male rostrum ( Figure 24 ). The top 20% of males had rostrum widths that were wider than the pronotum width of 50% of females.

Figures

FIGURE 1. Distribution of known Proterhinus species

FIGURES 2–5. Habitus photographs of Proterhinus tauai new species. 2, 4: female. 3, 5: male. Scale bars = 1 mm.

FIGURES 6–7. Head and rostrum of Proterhinus tauai new species. 6: female. 7: male. Scale bars = 0.5 mm.

FIGURES 8–9. Diagrams of head and rostrum of Proterhinus tauai new species, with dashed lines showing where measurements were taken. 8: female. 9: male. Basal width =. Distal width =. Rostrum length =. The circumscribed circle of forming the basis of the calculation of male rostrum area is shown as a dotted line with green fill.

FIGURES 10–18. Genitalia of Proterhinus tauai new species. 10: male tergite 8, dorsal view, showing rectal loop; 11, ae- deagus, dorsal view (tegmen coloured blue, tectum yellow, pedon red); 12, aedeagus, lateral view (tegmen coloured blue, tectum yellow, pedon red); 13, male sternite 8, ventral view; 14, female tergite 8, lateral view, showing rectal loop; 15, ovipositor, lateral view; 16, female tergite 8, dorsal view, showing rectal loop; 17, ovipositor, dorsal view; 18, female sternite 8, ventral view. Scale bar = 0.5 mm; all figures to same scale.

FIGURES 19–20. Habitat of Proterhinus tauai new species. 19: coastal scrub in northwest Miti‘aro. 20: Suriana maritima parasitised by Cassytha filiformis.

FIGURES 21–22. Allometric relationships of two traits with body length. 21: Distal width of rostrum. Regression lines are fitted separately for males and females. 22: Pronotum width. Regression line indicates the best fit for males and females com- bined. Dark blue squares indicate males, light blue circles females.

FIGURES 23–24. Relationship of male and female traits. 23: Boxplots showing the distribution of the pronotum width and elytral width of females and distal rostrum width of males. 24: Cumulative probability plot showing the overlap between male distal rostrum width and female pronotal width. Shaded area indicates zone of overlap between the two traits.