Arigumo (English spelling) ant mimicking spider

This spider belongs to the Arthropoda phylum, Arachnidae class, Araneae order, Salticidae family. Its body length, including its long jaws, is 7-9 mm. Its body color ranges from black-brown to reddish brown. At first glance it resembles an ant, with a slight constriction between the head and thorax, and its first leg looks like an antenna, so you won't realize it's a spider until it descends, pulling a thread. It mainly wanders around on the leaves of trees. It doesn't spin webs, but when laying eggs it makes a temporary home and birthing chamber out of thread. It is considered a good example of mimicry because it resembles an ant, but it is not clear what purpose this serves for the spider itself. It is widely distributed in Japan, and other spiders include the long-bodied ant spider, and the stag ant spider, which has a branch halfway up its fangs.

[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ハエトリグモ科に属するクモ。体長は長いあごを加えると7～9ミリメートル。体色は黒褐色から赤褐色。一見アリに似て、頭と胸の間は少しくびれており、第1脚が触角にみえ、糸を引いて下りるまでクモと気がつかないほどである。おもに樹木の葉の上を徘徊(はいかい)する。網を張らないが、卵を産むときに一時的に糸で住居兼産室をつくる。アリに似ているので擬態のよい例とされているが、クモ自体にそれが何に役だつのかははっきりわかっていない。日本に広く分布しており、ほかに体の細長いヤサアリグモ、牙(きば)の途中に枝のあるクワガタアリグモなどがいる。

［八木沼健夫］

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