Rhyparus helophoroides Fairmaire, 1893

Rhyparus helophoroides Fairmaire, 1893 View in CoL

Figures 32–33 View FIGURES 28–33

Rhyparus helophoroides Fairmaire, 1893: 145 View in CoL . Type locality: “ Bornéo occ., Sambas; Java, Simpar et Kemanglen , rés. Tegal ”.

Rhyparus helephoroides [sic] Fairmaire. Schmidt 1910: 91; and other authors.

Rhyparus amamianus Nakane, 1956: 123 View in CoL . Type locality: Japan, Amani Ōshima, Sumiyo. Ochi 2001: 2–3 (synonymy).

Rhyparus australiae Lea, 1923: 19–20 View in CoL . Type locality: Australia, Queensland, Cairns District. Stebnicka 1998: 845 (synonymy).

Rhyparus orousseti Paulian, 1981: 111–112 View in CoL , fig. 1c. Type locality: Philippines, Luzon, Mountain Province, Baguio. Stebnicka 1998: 845 (synonymy).

Rhyparus risbeci Paulian, 1934: 220 View in CoL . Type locality: “ Nouvelles-Hébrides ” [ Vanuatu]. Stebnicka 1998: 845 (synonymy).

Diagnosis. A member of the genus Rhyparus distinguished by the length 3.2–4.5 mm ( Fig. 32 View FIGURES 28–33 ). Body elongate, elytra laterally rounded, surface weakly glossy, dark reddish brown to black; pronotal and elytral costa well defined. Head surface with small, scattered punctures; anterior clypeal margin with obtuse tooth on each side. Pronotum with median intercostal area bearing scattered coarse punctures on entire surface; posterior half of lateral intercostae impunctate or with minute punctures; costa distinct along anterior margin; anterior and medial lobes on lateral margin distinctly triangular, prominent, anterior lobe slightly less prominent than median lobe. Elytra with intercostae flattened, each with two rows of large, deep, circular punctures, distance between rows of punctures narrow; trichome between caudal swellings of costae and caudal bulb small; caudal bulb rounded dorsally, with shallow depression separating weak internal and external lobes. Metaventrite with scattered coarse punctures on surface, distinct median groove and post mesocoxal pits present, lateral surfaces lacking fovea. Abdominal ventrites 2–5 with deep, strongly crenate anterior groove, ventrites with triangular fovea on each side; surface of ventrites 2–4 with fine punctures, ventrite 5 with scattered coarse punctures; ventrite 5 of male with strong median carina from anterior to posterior margin ( Fig. 33 View FIGURES 28–33 ), female with remnant carina on anterior half. Mesotibia of male with inner margin curved to prominent apical tooth; mesotibia of female with inner margin nearly straight, lacking apical tooth. Metatibia of male with inner margin swollen at basal third, then flattened or concave to apex, which lacks an inner apical tooth; metatibia of female with similar curvature, but much less pronounced. Mesotarsus and metatarsus setose ventrally, not dense, surface visible.

Distribution. Indonesia, Malaysia, Philippines, Taiwan, Japan, Korea, Papua New Guinea, Australia, the Solomon Islands, New Caledonia, and Vanuatu ( Stebnicka 1998; Ochi 2001; Théry & Bordat 2012; Ochi et al. 2021; Choi & Lim 2022; Anichtchenko et al. 2022; Minkina et al. 2025). To this list we add American Samoa and Samoa, and several islands from Vanuatu. This species was initially reported in Vanuatu [ New Hebrides] as “ R. risbeci Paulian, 1934 ”, without a specific locality or island being named.

Material examined (95 Total). The following from the study region: NEW CALEDONIA: Northern Province: Aoupinie, top camp, 21°10’44”S, 165°18’10”E, 750 m, 3.XI.2001, G. Monteith, mercury vapor lamp (1 QMA) GoogleMaps ; Tiakan Beach , 21°2’20”S, 165°24’13”E, 5 m, 30.IV.2005, G. Monteith, mercury vapor lamp (6 QMA) GoogleMaps ; Southern Province : Pocquereux, near La Foa, 23–29.I.2005, P. Jolivet, at light (3 FSCA) ; Pocquereux , near La Foa, 350 m, 27.I.2005, P. Jolivet, night gleaning (1 FSCA) ; Farino Refuge , 21°38’56”S, 165°46’54”E, 220 m, 3.V.2005, G. Monteith, mercury vapor lamp (1 QMA) GoogleMaps .

VANUATU: Ambrym Island: 22.VIII-4.IX.1967, J. & M. Sedlacek (19 BPBM, 2 FSCA) ; Efate Island: Villa , VIII.1950, N.L.H. Krauss (1 BPBM) ; Espiritus Santo Island: [no further locality] 2.III.1945, R.W. Alrutz, INHS 850,485 (1 INHS) ; [no further locality] 6.III.1945, R.W. Alrutz, INHS 850,478 (1 INHS) ; Cumberland Peninsula, low Penaoru River at 14.9611°S, 166.6331°E, 100 m, 27.XI.2006, R. Kitching, ultraviolet light IS100B (sub) (1 FSCA) GoogleMaps ; Cumberland Peninsula, low Penaoru River at 14.9611°S, 166.6331°E, 100 m, 25.XI–1.XII.2006, A.K. Tischenkin AT784, lights at camp, (1 CSCA, 1 FSCA) GoogleMaps ; Tanna Island: Lenakel , 0–200 m, I.1981, N.L.H. Krauss (1 BPBM) ; Pentecost Island: 4–5.IV.1964, R. Straatman, light trap (1 BPBM) .

AMERICAN SAMOA: Tutuila Island: Fagatoga , 1.XI.1963, N.R. Spencer (2 BPBM) ; Fagatoga , 4.XI.1963, N.R. Spencer (1 FSCA) ; Fagatoga , 30.XII.1963, N.R. Spencer (1 BPBM) ; Fagatoga , 10.I.1964, N.R. Spencer (1 BPBM) ; Pago Pago , 11.X.1963, N.R. Spencer (1 BPBM) ; Tafuna , 6.VII.1964, N.R. Spencer (1 BPBM) ; Tafuna , 22.IX.1964, N.R. Spencer (2 BPBM) ; Tafuna , 13.X.1964, N.R. Spencer (2 BPBM) ; Taputimu , 29.X.1963, N.R. Spencer (1 BPBM) ; Taputimu , 7.XI.1963, N.R. Spencer (1 BPBM) ; Taputimu , 5.XI.1963, N.R. Spencer (1 BPBM) ; Taputimu , 8.XI.1963, N.R. Spencer (2 BPBM) ; Taputimu , 26.XI.1963, N.R. Spencer (1 BPBM) ; Taputimu , 4.II.1964, N.R. Spencer (1 BPBM) ; Taputimu , 13.II.1964, N.R. Spencer, light trap (1 FSCA) ; Taputimu , 4.III.1964, N.R. Spencer, light trap (1 BPBM) ; Taputimu , 23.III.1964, N.R. Spencer, light trap (1 BPBM) ; Taputimu , 25.III.1964, N.R. Spencer, light trap (2 BPBM) ; Taputimu , 24.VI.1964, N.R. Spencer (1 BPBM) ; Taputimu , 25.VI.1964, N.R. Spencer (1 BPBM) ; Taputimu , 29.VI.1964, N.R. Spencer (1 BPBM) ; Taputimu , 13.X.1964, N.R. Spencer (3 BPBM) .

SAMOA: Upolu: Afiamalu , III.1962, R.W. Taylor, at light trap (1 MCZ) ; [Apia], Alafua , 6.I.1970, P.A. Maddison, at light (1 NZAC) ; [Apia], Moto’otua , 11–12.XI.1975, P.A. Maddison, mercury vapor light (2 NZAC) ; [Apia], Nafanua , 20.II.1975, P.A. Maddison, mercury vapor light (1 NZAC) ; [Apia], Utumapu [road near Fagali’i Airport], 16.VII.1971, P.A. Maddison, mercury vapor lamp (2 NZAC) ; Utumapu , 26.VII.1971, P.A. Maddison, mercury-cadmium-zinc lamp (1 FSCA) ; Utumapu , 20.IX.1971, P.A. Maddison, super actinic lamp (2 FSCA, 1 NZAC) ; [Apia], Viavase [road near Fagali’i Airport], 1.II.1971, P.A. Maddison, at light (1 FSCA) ; Viavase , 10.IV.1973, P.A. Maddison, super actinic lamp (6 NZAC) ; Viavase , 10.VI.1973, P.A. Maddison, mercury vapor 500 w lamp (3 NZAC) ; Faleanniu [handwritten, Faleasiu?], 12.V.1973, P.A. Maddison, super actinic lamp (4 NZAC) .

Comments. The three species here recorded from Samoa ( A. samoaensis , R. breviceps , and R. helophoroides ) extend the Rhyparini over 1000 km east from the nearest endemic members of the tribe in Fiji. Notably, the Samoan record for R. helophoroides is over 2200 km east of the previous record in Vanuatu, while R. breviceps is over 3000 km east from its report in the Solomon Islands ( Minkina et al. 2025).

Rhyparus breviceps and R. helophoroides are known from multiple island groups, that are widely separated from Samoa. Considering the collection dates in Samoa of both species, with none prior to 1960 and so many after that, it seems likely that one of two things may have happen: 1) a lack of collecting efforts in the region prior to the 1960s, or 2) the species recently immigrated to the islands and established. During and after World War II, there was a strong allied presence and movement between islands in the lower Pacific Theatre. This included activities between the Solomon Islands, Samoa, and many island nations between.

Being described four times in various regions may illustrate the movement of R. helophoroides and its recognition after arrival. Most species of Rhyparus are usually more regionally restricted. Other inquilines with social insects are known to have followed their hosts or to possibly shift to native hosts after arrival. Two examples of inquiline Coleoptera immigrations into the North America are Martineziana dutertrei (Chalumeau, 1983) ( Scarabaeidae : Aphodiinae ; Woodruff 1973) and Trichoideus desjardinsi Guérin-Méneville, 1838 ( Endomychidae : Pleganophorinae; Skelley & Burgess 1995).

These facts would indicate that R. breviceps and R. helophoroides could have recently migrated with human help and are not native to Samoa. Although not presently known from Fiji, R. helophoroides is expected to be found there and on other islands in the region.