うまのすずくさ (馬の鈴草) [Index] [Back] わが国の本州から四国・九州、それに中国の中東部から中南部に分布しています。山地の雑木林や湿潤な谷間に生え、蔓性で長さ２〜３メートルになり、他の植物などに絡みつきます。全草は無毛で粉白色を帯び、臭気があります。葉は厚い紙質で三角状卵形、基部は心形で両側が耳状に張り出します。６月から９月ごろ、葉腋に花を１個、まれに２個咲かせます。花弁はなく、３個の萼が合着して萼筒を形成します。萼筒は黄緑色で、内面は紫褐色です。果実は球形から楕円形の�刮ﾊで、わが国ではまれにしか結実しないといいます。本種は「じゃこうあげは（麝香揚羽）」の幼虫の食草です。幼虫は葉を食べながら体内にその毒を溜めこみ、これで鳥などの天敵から身を守っています。中国語では「馬兜鈴（ma dou ling）」と呼ばれます。 ウマノスズクサ科ウマノスズクサ属の多年草で、学名は Aristolochia debilis。英名は Slender Dutchman's pipe、Chinese Dutchman's pipe。 The Slender Dutchman's pipe (Aristolochia debilis) belongs to Aristolochiaceae (the Birthwort family). It is a perennial herb that is distributed throughout Japan, from Honshu to Shikoku and Kyushu, as well as from the central-eastern to central-southern regions of China. It grows in mixed forests in mountainous areas and in humid valleys; it is a vine that grows to 2-3 m in length and twines around other plants. The entire plant is hairless, has a whitish-powdery appearance, and emits a distinctive odor. The leaves are thick and papery, triangular-ovate in shape, with a heart-shaped base and ear-like projections on both sides. From around June to September, it produces one flower-rarely two-in each leaf axil. It has no petals; the three sepals are fused to form a calyx tube. The calyx tube is yellowish-green, with a purplish-brown interior. The fruit is a spherical to elliptical capsule; it is said to bear fruit only rarely in Japan. This species is the food plant for the caterpillars of the "Chinese windmill". As the caterpillars feed on the leaves, they accumulate the plant's toxins in their bodies, which they use to protect themselves from natural enemies such as birds. It is called "馬兜鈴" (ma dou ling) in Chinese. 宮城県仙台市太白区秋保町馬場「秋保大滝植物園」にて、2026年07月28日撮影。 Shu Suehiro shu@botanic.jp