ホシザキグリーン財団研究報告特別号 第32号: 9 ― 12 頁，2023 年 1 月
Spec. Bull. Hoshizaki Green Found.（32）: 9 ― 12，Jan. 2023

A Record of Leptelmis torikaii Larva from Amami-Ôshima,＊Ryukyu, Japan（Coleoptera, Elmidae）
Masakazu HAYASHI 1）and Takafumi MORII 2）
Hoshizaki Green Foundation, Sono 1664 ― 2, Izumo, Shimane Pref., 691 ― 0076 Japan

1）

Aichi Prefectural Federation of Land Improvement Association, 1 ― 18 ― 25, Sakô, nishi-ku,

2）

Nagoya, Aichi Pref., 451 ― 0052 Japan
Abstract One larval specimen of Leptelmis torikaii Kamite, Yoshitomi et Hayashi,2017 was obtained by rearing that the adults were collected from Amami-ÔshimaIsland, Kagoshima Prefecture, Japan. The larva resembles Leptelmis gracilis Sharp,
1888 but the morphology of the lateral projections on abdominal segments I to VIII
are useful for their identification.
Key words：aquatic beetles, identification, Nansei Islands, riffle beetles

A riffle beetle, Leptelmis torikaii Kamite, Yoshitomi et Hayashi, 2017 is distributed in AmamiÔshima, Ryukyu（Nansei Islands）, Japan, is 2.2 ― 2.6 mm long, and inhabits streams（Kamite et al.,2017）. The body color of the adult is black, with reddish brown on the ventral side and legs（Kamiteet al., 2017）. However, the larvae have not yet been discovered. The genus Leptelmis include 17species from South Asia to East Asia（Jäch et al., 2016）. The larva of this genus is characterized bya flat body but it known only a subspecies, Leptelmis gracilis gracilis Sharp（Hayashi and Yoshitomi,2014; Kamite et al., 2017）that is distributed in the main islands of Japan（Honshu, Shikoku, andKyushu）and Korea.
The larva was obtained by laboratory rearing of adults collected on August 21, 2017, fromTatsugo-chô, Amami-Ôshima Island, Kagoshima Prefecture, Japan, by the second author（T.
Morii）. The adults were placed in a transparent plastic container（H 47 × W 112 × L 158 mm）. At
the laboratory in Ichinomiya-shi, Aichi Prefecture, Japan, the container was filled to a depth of 25
mm with water, sand, and Java moss. Room temperature was not controlled. Larva was found in thecontainer on March 28, 2019, and fixed with ethanol on April 11, 2019.
The specimen is a mature larva, and its morphological features（Figs. 1 and 2）are as follows:
Body right brown, head and abdominal segment IX partly black; body flat in prothorax to abdominal
segment VIII; abdominal segment IX slender, with longitudinal ridge and small spines in apex;
prothorax longer than width, meso- and meta-thorax wider than length, each abdominal segment I
to VIII wider than length; outer basal angle of each segment（abdominal segments I to VIII）slightlyextending behind.
In describing larvae, it is necessary to examine the mouth parts and the microstructure of thebody surface. Since only one specimen is available at this time, a detailed study is needed in the＊ホシザキグリーン財団研究業績

第 370 号

9Masakazu HAYASHI and Takafumi MORII

Fig. 1. Larva of Leptelmis torikaii. A ― D. dorsal view; E ― G. ventral view. Scale bar ＝ 1.0 mm.

10A Record of Leptelmis torikaii Larva from Amami-Ôshima, Ryukyu, Japan（Coleoptera, Elmidae）

A

B
1.0mm

Fig. 2. Larva of Leptelmis torikaii. A. dorsal view; B. ventral view.

future. We hope that additional larvae will be discovered.
Key to species of Japanese Leptelmis larvae
1．Outer basal angle of each segment（abdominal segments I to VIII）slightly extending behind…………… Leptelmis torikaii Kamite, Yoshitomi et Hayashi
2．Outer basal angle of each segment（abdominal segments I to VIII）strongly extending laterally………… Leptelmis gracilis Sharp

References
Kamite, Y., H. Yoshitomi and M. Hayashi（2017）A remarkable new species of the genus Leptelmis
Sharp from Amami-Ôshima, with redescription of the larva of Leptelmis gracilis Sharp（Coleoptera, Elmidae, Elminae）. Elytra, Tokyo, New Series, 7（2）: 395 ― 408.
Hayashi, M. and H. Yoshitomi（2014）Taxonomic treatments of two Japanese elmid beetles,
Stenelmis vulgaris Nomura and Leptelmis gracilis Sharp（Coleoptera: Elmidae）, withdescriptions of their larvae. Japanese Journal of Systematic Entomology, 20（2）: 235 ― 244.
Jäch, M. A., J. Kodada, M. Brojer, W. D. Shepard and F. Čiampor（2016）Coleoptera: Elmidae andProtelmidae. World Catalogue of Insects, 14. XXI ＋ 318 pp. Leiden, Brill.

11

Masakazu HAYASHI and Takafumi MORII

アマミヨコミゾドロムシ幼虫の初確認（コウチュウ目ヒメドロムシ科）
林成多・森井隆文

アマミヨコミゾドロムシ Leptelmis torikaii Kamite, Yoshitomi et Hayashi, 2017 は，奄美大島に分布するヨコミゾドロムシ属の一種である．本種の幼虫は未確認であったが，著者の一人である森井が成虫を飼育したところ，飼育容器内で繁殖したと考えられる老熟幼虫を 1 頭得ることができた．本種の幼虫は，本土側に分布するヨコミゾドロムシ Leptelmis gracilis（Sharp, 1888）と同様に平坦な体型をしており，この体型はヨコミゾドロムシ属の特徴と考えられる．観察可能な標本が少ないため，口器等の解剖を伴う詳細な観察はしていないが，ヨコミゾドロムシとは形態に違いが見られた．具体的には，腹部腹節（第 1 節から第 8 節）の後角がヨコミゾドロムシでは側方（後ろ斜め）へ強く突出するのに対し，アマミヨコミゾロムシでは後方に弱く尖る程度である．
キーワード：水生甲虫，同定，南西諸島，ヒメドロムシ

12