Kimura Gumo Spider, Heptathela kimurai

The Kimura Gumo or Kimura Spider (Heptathela kimurai) is an Old World spider, located mainly in Japan and named after Kimura Arika, who discovered the spider in 1920. It belongs to the sub-order Mesothelae, a group of primitive burrowing spider, and can reach up to 3 centimeters long. Their burrows are covered by a camouflaged “pill box” flap.

The ancestral characteristics of this spider include central spinnerets and signs of segmentation on the abdomen. These features aren’t seen on modern spiders, therefore studying the Kimura Gumo can shed light upon the evolution of all spiders.

Though these spiders lack venom glands, they still have strong chelicerae and can yield rather painful bites.

The word kumo in the Japanese language means spider. The sub-order that this spider is a member of, Mesothelae, is about 400 million years old, putting the kimura spider among the most primitive living spiders. The spinnerets are located in the middle of the body, rather than to the more efficient location in modern spiders at the rear of the abdomen. It fixes eggs on the surface of its burrow with silk so that they are well protected. The spider surrounds tunnels with a cobweb, as well. When it leaves for hunting, it pays out a line of silk behind it this “lifeline” aids in orienting itself.

Image Caption: female Heptathela yanbaruensis (previously Heptathela kimurai yanbaruensis) from Okinawa. Credit: Akio Tanikawa/Wikipedia (CC BY-SA 2.5)