From the Super Mario Wiki
Kumos are hopping spider enemies found in Easton Kingdom in Super Mario Land. They are only found in World 3-2. In appearance, Kumos look much like generic tarantulas that are about the size of Mario.
Kumo (「クモ」) is the Japanese word for "spider"; however, the species is not, in fact, known as "Kumo" in Japan. It is actually the only species for which the English name was not the same as or similar to the Japanese name in the original version of Super Mario Land, although other species were renamed in the Virtual Console port.
Kumos attack in the exact same pattern as a Fly, hopping around until it comes in contact with Mario. A jump or two superballs can easily defeat it, rewarding Mario with 400 points.
A Kumo also makes a small appearance in the Nintendo Adventure Book Pipe Down!, although only a picture of it appears.
A darker variety with a blue mouth
A normal Kumo on the left, a stomped Kumo on the right
Names in other languages
|Black Piyon (manual source)|
Black Pyon (website source)
From pyonpyon, a mimetic word for hopping.
Therefore, the former spelling was likely a typo.