Jewel beetles (Coleoptera, Buprestidae) collected during the 2018 field survey on Iejima Island, the Okinawa Islands, Ryukyus, south-western Japan

Abstract Background Only one jewel beetle, Chrysodema (Marcsikiella) dalmanni (Eschscholtz) (Coleoptera, Buprestidae) has hitherto been recorded from Iejima Is. in the Okinawa Isls., Ryukyus, south-western Japan. New information A total of seven jewel beetles were collected on Iejima Is. The following six species are newly recorded from the island: 1) Paratrachys princeps chujoi Kurosawa, 2) Chrysodema (Chrysodema) lewisii Saunders, 3) Chalcophora japonica oshimana Schönfeldt, 4) Coraebus hastanus Gory and Laporte, 5) Sambus quadricolor quadricolor Saunders and 6) Agrilus okinawensis shiozakii Tôyama.


Introduction
The Okinawa Islands in the Ryukyus, south-western Japan (Fig. 1) has one of the highest species diversity of jewel beetles (Coleoptera, Buprestidae) in Japan. From the islands, 44 buprestid species belonging to 18 genera in four subfamilies have hitherto been recorded, including five endemic species and five endemic subspecies (Ohmomo andFukutomi 2013, Hattori 2014). This species number accounts for about 20% of all Japanese buprestid beetles. The buprestid fauna of the Okinawa Isls. has hitherto been well surveyed particularly in the largest island, Okinawajima Is. (area ca. 1,207 km ; 44 known species), while our knowledge on the fauna of the other islands is still limited due to the lack of sufficient surveys. For example, only eight species had been recorded from the second largest island, Kumejima Is. (area ca. 60 km ) until recently, when five more species were recorded by .
Iejima Island, about 9 km off the north-western coast of the Motobu Peninsula in Okinawajima Is., is the third largest island (area ca. 22.8 km ) in the Okinawa Isls. (Fig. 1). Iejima Is. is mostly flat and covered with cropland, except a small evergreen broad-leaved forest is spreading in Mt. Gusuku-yama (altitude ca. 172 m), located in the central east (Figs 1, 2). Presently, only one buprestid beetle, Chrysodema ( Marcsikiella) dalmanni (Eschscholtz, 1837), is known from the island (Kohama 2015, Yao 2016). However, more buprestids are expected to occur on the island, since no investigations on the buprestid fauna have been conducted until now. In June 2018, we conducted a field survey on Iejima Is. and collected seven buprestid beetles, six of which are new to the fauna of the island. In this paper, we will report them for the first time from Iejima Is. Location of the Okinawa Islands and Iejima Island in the Ryukyus, south-western Japan.

Materials and methods
Specimens used in this study were collected on Iejima Is. by the authors in a period from 8 to 11 June 2018. All the specimens were collected by net-sweeping or beating of plants, as well as by visual searching and then examined and identified by the first author (YT) under an Olympus SHZ10 stereomicroscope. In addition, associated plants with each buprestid species were identified by him. Scientific names of buprestid beetles followed recent catalogues edited by Löbl and Löbl (2016) and plant nomenclature followed Yonekura and Kajita (2003). Finally, all the specimens are preserved in the private collection of the first author.
A habitus photograph of each species was taken under a Canon 8000D digital camera. Each final image was assembled from a series of photographs with different focus planes, using the computer freeware CombineZP (Hadley 2010).
Abbreviations used for collector names in this study are as follows: HY -Hiraku Yoshitake; YT -Yutaka Tamadera.

Notes
New to Iejima Is., these specimens were collected by visual searching and beating Ficus pumila (Moraceae) which grows on a cliff facing the sea (Figs 3d, 4a).

Notes
New to Iejima Is., these specimens were collected by visual searching and netsweeping Elaeocarpus zollingeri (Elaeocarpaceae) and Toxicodendron succedaneum (Anacardiaceae) (Fig. 3a, f). Toxicodendron succedaneum is not recorded as a host plant of C. (C.) lewisii, but this species may be associated with the plant at least during the adult stage, because some specimens were collected from it at several places.

Notes
New to Iejima Is., these specimens were collected by net-sweeping Pinus luchuensis (Pinaceae). The collecting site is a small forest left in cropland (Figs 4c, 5a). a b c d Figure 5.

Notes
New to Iejima Is., these specimens were collected by visual searching and netsweeping Macaranga tanarius (Euphorbiaceae) which is not recorded as a host plant of C. hastanus (Figs 3b, 4d, 5b). This buprestid beetle is almost certainly associated with M. tanarius, because all specimens were collected only from the plant. In addition, Mallotus japonicus (Euphorbiaceae), which has been known as a host plant of this species, was not found in and around each collecting site, as far as we searched.  Kusui and Miyagi 2017).

Notes
New to Iejima Is., these specimens were collected by visual searching, net-sweeping and beating Ficus pumila which grows on an artificial wall (Figs 3c, 4e, 5c).

Discussion
By this study, the number of buprestid beetles, known from Iejima Is., has been increased from one to seven species belonging to six genera in three subfamilies. Amongst them, four species, Chrysodema ( Marcsikiella) dalmanni, Chrysodema ( Chrysodema) lewisii, Chalcophora japonica oshimana and Coraebus hastanus, are common species and broadly distributed in the Okinawa Isls. (Table 1), since their associated plants are also common and abundant in many islands. With regard to Chalcophora japonica oshimana, marine drifts might have played a role in the dispersal of the species from island to island in the Okinawa Isls. (Kurosawa 1974 Generally, larger islands tend to have more species, while smaller islands tend to have fewer species (Whittaker and Fernández-Palacios 2007), but the number of buprestid species presently known from Iejima Is. is less than that from some smaller islands in the Okinawa Isls. (Table 1). Probably due to excessive deforestation in Iejima Is., the buprestid fauna of this island seems to have become considerably poorer than in the past. However, it is still possible that some additional buprestids will be found on Iejima Is., since our field survey was conducted during a short period in the early summer of 2018. Table 1.
Commonality of buprestid species between Iejima Island and some other islands of the Okinawa Islands (area (km ) of and the number of known species from each island are indicated in parentheses). 2