Like many creatures once thought capable of haunting a place or bewitching a person, the jorōgumo is a quite real animal recognized by modern zoology. The name is now given to the tetragnathid spider Nephila clavata, but long ago it was considered the same as the araneid kogane-gumo (genus Argiope). Both are large orb-weaving spiders with attractive markings. Other names considered equivalent were madara-gumo, and the Chinese moniker rakushinpu (luò xīn fù). Although today this type of spider is known not be venomous, in former times it was thought to carry dangerous poison along with its supernatural inclinations. The famous Edo period encyclopedia, the Wakan Sansai Zue 和漢三才図会 says of the jorōgumo:

絡新婦とは谷に女郎蜘蛛と称するもので、黄　・　黒　・　緑　・　赤の斑が
美しいが、かえって醜い。毒が最もはなはだしいせいである。形は
（普通の）　蜘蛛より長く、細い腰、尖った尻に手足は長く黒い。糸は黐
（とりもち）のように粘くって黄色をおびており、樹枝や家の檐に網をはる。
人が捕えて打つと脆くつぶれて血を出して死ぬ。他の蜘蛛は血を持って
いない（体液が赤くないということ）。尻が尖りその二ヵ所は動揺するに
つれてぴかぴか光る。けれども蛍火　（ほたるび）　のように鮮やかでない。
老いたものはよく火を生じる。闇夜、あるいは微雨の中でたまたまこれを
見ることがある。
The rakushinpu is a thing which takes the name of jorōgumo in the valleys, and its yellow, black, green and red speckles are beautiful, but on the contrary it is ugly. Its poison is extremely terrible. In form, compared to a [usual] spider, it has a long, slender back, and a pointed rear end with long black limbs. Its thread is sticky like bird-lime and is tinged with yellow, and it makes its webs in the branches of trees and the eaves of houses. If a person seizes and strikes it will be brittlely smashed and it will bleed and die. Other spiders do not have blood [their bodily fluids are not said to be red]. Its rear end is sharp and in two places it oscillates and sparkles. However it is not as vivid as the light of a firefly. Old things often produce light. At times it is unexpectedly seen on a dark night, or in a light rain. ¹

The Ming Dynasty medical tome Běncǎo Gāngmù 本草綱目 also mentions the luò xīn fù, describing how a man was bitten on top of the head by the spider, and after his head swelled up immensely he was cured by a topical concoction made of "great indigo juice" 大藍汁, "musk" 麝香, "male yellow" 雄黄, and a single spider. ²

In folklore the jorōgumo is often associated with the supernatural "masters" (nushi 主) of deep pools and waterfall basins. A common folktale motif tells how, while a man is resting near waterfall or pool, a spider (often a jorōgumo) appears and attaches a thread to his leg or toe. The man, though not too flustered, thinks this is strange and reattaches the thread to an old stump, only to watch in horror as the stump is pulled into water by a water-spirit intent on eating the man.³

The master of Jōren Falls 浄蓮の滝 (in Amagiyugashima Town 天城湯ヶ島町 on Shizuoka Prefecture's Izu Peninsula 伊豆半島) is popularly considered to be a powerful jorōgumo. Local legend says this spider once wound a thread around a peasant's leg and then, with a great thundering sound attempted to drag him into the falls, thwarted only by the man transferring the thread to a mulberry stump beforehand. ⁴

The Izu Densetsu Shū (伊豆伝説集, Izu Legend Collection) includes an expanded version of this story, in which the jorōgumo shows up again much later to a woodcutter who has dropped his hatchet into the water. The spider appears in the form of a beautiful woman from between the rocks, who returns the hatchet and tells the man that she is the jorōgumo master of the falls, and that he must never tell anyone that he met her or he will lose his life. Some time later the woodcutter gets drunk at a teahouse and, as the other people are entertaining each other with ghost stories concerning waterfalls, he repeats his own experience. Afterwards he drinks himself to sleep and does not wake up. ⁵

In Hanawa Town 塙町, Higashishirakawa District 東白川郡, Fukushima Prefecture, a similar story is told about a place called Maeda Falls 前田滝 (now replaced with a powerplant). Here the "water tiger" (suiko, a name roughly synonymous with the kappa) uses a "large spider" to attach a thread to the thumb of a man, who foils the plot by attaching the thread to a soba tree's root.⁶

Jorōgumo haunting is also the subject of some Edo period ghostly literature.

In the Tonoi-gusa 宿直草, a young samurai takes shelter for the night in an old Shinto shrine, only to encounter a strange woman who holds out her child to him and insisting he is its father. The man glares and fingers his sword, assuming this unlikely pair are the trick of some bakemono, but hesitates until the mother comes for him herself. When he strikes the strange woman, she scampers up onto the ceiling of one of the shrine's buildings. In the morning the man inspects the ceiling and finds the dead, sword-slashed body of an enormous jorōgumo spider, surrounded by human corpses. He realizes also that the "child" had been nothing but a stone gorintō stupa, and if he had struck at it his sword would have broken and rendered him helpless. ⁷

In the Taihei Hyaku Monogatari 太平百物語, a wealthy rural bushi named Sonroku builds himself a second house in which to calm his nerves and recite poetry. One day an old woman approaches him, saying her daughter listens to him every day and is pining with love for him, and leads him to the courtyard of a strange house with many doors. The beautiful daughter emerges and begs him to stay with her as her husband, but he refuses, as he thinks he is in too low a social position for a woman of such high breeding and already has a wife, besides. Her insistent begging eventually becomes too much for him to bear and he flees, at which point the strange house vanishes and he is back on his own veranda. When asked, a servant claims Sonroku had been sleeping the whole time. The bushi then notices a jorōgumo spider dropping from the ceiling. He remembers the strange girl attempting to guilt-trip him because he had tried to kill her mother with a kiseru pipe just the other day, when he had in fact used his pipe to try to drive a spider away. Realizing the many spiders on the ceilings are invading his dreams, he has the servant gather them and their webs up and discard them in a distant field, after which he is plagued by no more strange events. ⁸


Sources:
• Tada, Katsumi 多田克己 and Natsuhiko Kyōgoku 京極夏彦. Hyakki Kaidoku 百鬼解読 (Deciphering the Hundred Demons). Tokyo: Kodansha, 2006. p 123-38.

Citations:
1. Tada p. 123. Scientific names for the spiders from Common Spiders in Japan: List of Spiders.
2. Tada p. 123-4.
3. Tada p. 134.
4. "Jorōgumo, Taki-no-nushi". Kaii-Yōkai Denshō Database 怪異・妖怪伝承データベース. Summary of: Kimura, Hiroshi 木村博. "Evil Spirits and Monsters 2: Strangeness on the Shore 悪霊と妖怪：２　陸の怪異". Shizuoka Prefecture History - Document 23 - Folk Customs 1 静岡県史　資料編23　民俗1. Shizuoka Prefecture: 1989. p 1096.
5. Tada p. 134-6.
6. "Taki no Nushi no Kumo 滝の主の蜘蛛." KYDD. Summary of: Tokyo Women's Christian University History Department Folk Customs Research Group 東京女子大学史学科民俗調査団. "Six Tales of Oral Literature 口承文芸　6伝説." The Folk Customs of the Interior Province of Higashirakawa: The larger upriver section of Hanawa Town, Higashirakawa District, Fukushima Prefecture 奥州東白川の民俗：福島県東白川郡塙町大字川上. 1971. p 10.
7. Tada p. 125-7.
8. Tada p. 128-132