Elateridae ( Insecta , Coleoptera ) from Tanegashima Island ( Ryukyu Islands , Japan )

There are few records of beetles of the family Elateridae from Tanegashima Island, in the Ôsumi Islands, in the Ryukyu Islands, Japan, and the elaterid fauna of this island has not been reviewed. We examined newly collected specimens and reviewed the previous records from the island. In field work and from a colleague’s collection, we found 27 species, of which 13 were recorded for the first time on the island. As result 43 species are confirmed from this island and a checklist of all elaterid species from Tanegashima Island is provided.


Introduction
Tanegashima Island is the easternmost Ôsumi Islands, in the northernmost part of the Ryukyu Islands of Japan.The island is the second largest of the Ôsumi Islands, covering 444 km 2 with a maximum elevation of 282 m (Geospatial Information Authority of Japan 2018, Kyushu Regional Forest Office 2018).Its vegetation is lowland laurel forest.The island occupies an important position biogeographically because it has a large lowland forest near the boundary between the Palearctic and Oriental regions.Chûjo (1973), Hirashima (1989), and Kishii (1999) listed 4, 10, and 16 species, respectively, of Elateridae from Tanegashima Island.Ôhira (1998a, 2000) recorded 9 species from the island and Ôtsubo (2013) reported 8 species as new records.Currently, approximately 30 species have been recorded from this island (Kishii 1999(Kishii , Ôhira 1996a(Kishii , 2000(Kishii , Ôtsubo 2013).In comparison, 639 elaterid species have been recorded from Japan (Ôba et al. 2015).
Moreover, there is discordance between information from the distributional records for Tanegashima Island and a checklist of the Japanese elaterid fauna (Kishii 1976b(Kishii , 1999(Kishii , Ôhira 2005(Kishii , Ôtsubo 2013).In this study, we examined newly collected specimens of elaterid beetles, reviewed the previous records, and provide a checklist of the species from Tanegashima Island.
(Garmin GPS Map 62s; map datum setting: WGS84) and rounded off to 4 decimal places (Table 1).Altitude was obtained from Google Earth Pro v. 7.3.0.3832 based on the recorded latitude and longitude.The specimens collected in our field work were deposited in the first author's collection and will be transferred to Osaka Museum of Natural History, Osaka, Japan.
Remarks.Quasimus uguriensis was divided into 3 subspecies: Quasimus uguriensis uguriensis Kishii, 1970 from Uguru Island, Shikoku; Q. uguriensis okicola Kishii, 1970 from Okinoshima Island, Shikoku; and Q. uguriensis heianus from Kuchinoerabu Island, in the Ôsumi Islands.The 3 subspecies are similar in the shape of the male aedeagus, but differ in the hind angle of the prothorax, scutellum, and metasternum (Kishii 1976a).The specimen examined is similar to the specimens of the type series of Quasimus uguriensis heianus in the shape of the scutellum (Kishii 1970) and differs from the type series by the sinuate hind angle of the prothorax and the carina of the metasternum obscure posteriorly.There are no detailed studies of morphological variation either among allopatric populations or among sympatric specimens because there are few records of this species.Future efforts to collect more specimens are needed to understand the morphological variation of this species.In this study, we determined that the specimens examined were Q. uguriensis heianus based on similar scutellum and its distribution.
Bionomics.The specimen examined was collected under a stone near the mouth of a river, together with Zorochros (Pronegastrius) humeralis yakuensis (Kishii 1976a).
Paracardiophorus pullatus pullatus exhibits variation in leg coloration, which can be black or yellow.The legs of 1 of the specimens examined were black, while those of the remaining 3 specimens were yellow.
Bionomics.The specimens examined were found in the spaces between small stones in the open space beside cultivated land near the seaside (Fig. 2B).Species diagnosis.Ôhira (1997a) Bionomics.At Site 10 (Fig. 2C), we observed, during the day, 32 specimens of Paracardiophorus sequens in 30 min, on leaves of Ipomoea pes-caprae (family Convolvulaceae) on a sandy beach.The insects did not move from the leaves during our observations.We also found one specimen of the false blister beetle Asessinia flavomarginata (Miyatake, 1985) and some Diptera and Hymenoptera.The Diptera and Hymenoptera specimens were observed flying actively and landing on leaves briefly.Only P. sequens seemed to occupy the leaves of I. pes-caprae.Each I. pes-caprae leave is typically folded at the mid-vein.Most of the specimens of P. sequens stayed in the shadow at the mid-vein thrown by the fold (Fig. 2D).Several specimens held onto stems.Usually, Paracardiophorus species tend to hide under or between stones (Arimoto 2014), while P. sequens hides near the roots of grasses or just under the surface of sandy ground on beaches where there are few stones (Arimoto 2016).We postulate therefore that this behavior helps the beetles to avoid the heat of the sand on the beach under the blazing sun.
We confirmed a total of 43 elaterid species from Tanegashima Island, including 13 newly recorded species (Table 2).There is no endemic species or subspecies from this Island.Thirty-nine species (90.7% of those from Tanegashima Island) are also distributed on Yakushima Island, which is located 18 km west of Tanegashima Island.
The Ôsumi Islands are the southern limit of the distribution of about 50 elaterid species (Arimoto unpublished data), and Yakushima Island is the southern limit of the distribution for almost all of them because Yakushima Island is located at south of Tanegashima Island.As result, Tanegashima Island is the southern limit of the distribution of only 3 species [Meristhus (Sulcimerus) niponensis Lewis, 1894; Parasilesis musculus musculus Candèze, 1873;and Glyphonyx illepidus Candèze, 1873].Ôtsubo (2013) recognized Tanegashima Island as the southern limit of the distribution of Ectinoides insignitus insignitus (Lewis, 1894), although the correct southern limit is Yakushima Island (Kishii 1999).Tanegashima Island is not the northern limit of the distribution of any elaterid species.
The elaterid fauna of Tanegashima Island has been characterized by the absence of species in elevated land or riversides until this study.A lack of research may have resulted in the absence of records from riverside species because we found 2 species under stones by a river: Quasimus uguriensis heianus and Zorochros (Pronegastrius) humeralis yakuensis.
Table 2. Checklist of species of the family Elateridae in Tanagashima Island, Japan.Asterisk (*) denotes new record from Tanegashima Island, dagger ( †) denotes Tanegashima Island as the southern limit of the species distribution, hash (#) denotes non-native species from Taiwan, and section make ( §) denotes sharing species with the elaterid fauna of Yakushima Island, which is located 18 km west of Tanegashima Island.

Figure 2 .Figure 3 .
Figure 2. A, B. Site 9. C, D. Site 10.E, F. Site 13.The site numbers correspond to those of Table 1. A. Gutter on the side of a road through cultivated land near the seaside.B. Open space beside cultivated land near the seaside.C. Sandy beach.D. Paracardiophorus sequens sequens (Candèze, 1873) on a leaf of Ipomoea pes-caprae (family Convolvulaceae).E. Sandy beach (arrow: rotting wood).F. Male of Suzukielater babai(Kishii and Ôhira, 1956) from rotting wood lying on a sandy beach.

Table 1 .
Collection sites of the material used in this study, Tanegashima Island, Japan.Map of the Ryukyu Islands, Japan. A. Location of Ôsumi Islands in the Ryukyu Islands.B. Map of Tanegashima Island of Ôsumi Islands, showing the collection sites of the material used in this study.The numbers correspond to the site numbers of Table1.
Kishii, 1970.negastrius (Pronegastrius) humeralis yakuensis based on specimens from Yakushima Island and assigned the Negastrius humeralis population from Yakushima Island to the subspecies name.Bionomics.The specimen examined was found under a stone near the mouth of a river, together with Quasimus uguriensis heianusKishii, 1970.