Ashidakagumo (English spelling) banana spider

This spider belongs to the Arthropoda phylum, Arachnidae family, and Araneidae family. The females are about 3 cm long and the males are about 2 cm long, making it the largest wandering spider in Japan. Its entire body is brown, and its legs spread out horizontally. It lives inside houses in the Pacific coastal areas south of the Kanto region. It is native to tropical regions, but has now spread all over the world by public transport. It can survive the Japanese winter thanks to indoor heating. It molts about 10 times and lives for several years before it grows, and there is a record of it being kept in captivity for 9.5 years. In summer, it makes a disk-shaped egg sac, which it carries with its palps and third leg. It is generally disliked because of its color, shape and size, but it is a beneficial insect that wanders around houses, becomes active in the evening, and actively preys on cockroaches. It is also interesting that the distribution of huntsman spiders and cockroaches is similar. In foreign countries, they are called banana spiders because they were often introduced in banana packages. This species includes the slightly smaller small-sized huntsman spider, which lives in dark places and caves outdoors, and in rural areas it sometimes sneaks into houses. The huntsman spider that appears in the Wakan Sansai Zue (1712) is the modern-day long-legged spider.

[Takeo Yaginuma]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

節足動物門クモ形綱真正クモ目アシダカグモ科に属するクモ。体長は雌3センチメートル、雄2センチメートルぐらいで、徘徊(はいかい)性のクモでは日本最大。全体が褐色で、脚(あし)は横に広がる。関東地方以南の太平洋沿岸地域の家屋内にすむ。原産地は熱帯地方であるが、現在では交通機関によって世界中に広まっている。屋内暖房のため日本の冬でも越せる。成長するまで10回ぐらい脱皮して数年生き、飼育例では9年半という記録がある。夏に円盤状の卵嚢(らんのう)をつくり、触肢と第3脚で抱えて持ち運ぶ。色と形と大きさから一般に嫌われているが、家屋内を徘徊し、夕方になると活動を始め、盛んにゴキブリを捕食する益虫である。アシダカグモとクロゴキブリの分布が似ているのもおもしろい。外国では、よくバナナの荷に紛れて移入したことからバナナグモとよばれる。この仲間には野外の薄暗い所や洞穴にすんでいる少し小形のコアシダカグモがおり、田舎(いなか)では家に入り込むことがある。なお『和漢三才図会』（1712）に出てくるアシダカグモは、現在のアシナガグモである。

［八木沼健夫］

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