Kuroshijimi - Black clam

A butterfly belonging to the family Lycaenidae in the order Lepidoptera of the class Insecta. It is distributed throughout Honshu, Shikoku, and Kyushu (including Tsushima), and its habitat is generally localized. Outside of Japan, it is found in the Korean Peninsula and China, and is endemic to East Asia. The wingspan is about 30-35 millimeters. The upper surface of the wings is blackish brown, with males having a strong dark purple luster, but females do not. The base color of the underside is off-white to dark gray, with sesame-like spots. The shape of the wings differs between sexes, with females being round and males being pointed. They emerge once a year, from June to August, and while males fly actively above the trees, females often fly slowly through the grasslands between the forests. This species of butterfly has a particularly unusual life cycle; young larvae grow by licking the honeydew secreted by aphids, but when they reach the third stage, black ants traveling up the trees become interested in the larvae, picking them up and carrying them back to their nests, where they raise them by feeding them by mouth. The larvae often emerge from beech-family trees such as oak and sawtooth oak, but are not picky about any particular tree species. The larvae spend the winter in their larval form inside ant nests.

[Takashi Shiramizu]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

昆虫綱鱗翅(りんし)目シジミチョウ科に属するチョウ。本州、四国、九州（対馬(つしま)を含む）に分布、その生息地は一般に局部的である。外国では朝鮮半島、中国に産し、東アジアの特産種。はねの開張は30～35ミリメートル程度。はねの表面は黒褐色、雄では暗紫色の強い光沢があるが、雌にはない。裏面の地色は灰白色ないし暗灰色、ゴマ状の斑点(はんてん)がある。はねの形は雌雄で異なり、雌では丸いが、雄ではとがる。年1回の発生、6～8月に出現、雄は樹上を活発に飛ぶが、雌は林間の草地を緩やかに飛ぶことが多い。本種はチョウのなかでも特別に変わった生活史をもつもので、若齢幼虫はアブラムシ類の分泌する甘露をなめて育つが、3齢になると樹上を往来するオオクロアリが幼虫に関心を示すようになり、これをくわえて巣に連れ帰り、以後口移しに餌(えさ)を与えて幼虫を育てる。幼虫の発生する木はブナ科のコナラ、クヌギが多いが、とくに樹種は選ばない。幼虫はアリの巣の中で幼虫態で冬を越す。

［白水　隆］

出典　小学館　日本大百科全書(ニッポニカ)日本大百科全書(ニッポニカ)について　情報 | 凡例