Ohmu are enormous invertebrates. Though they are ordinarily docile, killing any insect while in the Sea of Corruption will drive any nearby Ohmu into a berserk rage. Due to their great size, they can destroy entire settlements in this state, and the spores from forest plants which they scatter as they move can kill crops and render an area unsuitable for human life if left unchecked.
However, the molten exoskeletons of the creatures  are stronger than ceramics, capable of resisting most human weaponry, and thus highly sought-after as material for weapons, tools, and structures. The Ohmu possess a hive mind  with which certain sensitive persons may communicate.
The Ohmu are a unique creation. Their compassion is overwhelming yet at first appearance they seem to be bloodthirsty evil bugs. But the fact of the matter is that they love, and they care for their fellow Ohmu. They care for all living creatures, and they cry when they kill. They have no choice, when their eyes turn red with rage they go on a rampage, even though they don't want to harm anything they still do.
An Ohmu abandons its shell and skin every so often, and when injured, they bleed blue blood, and they have 14 eyes . They release spores that land on the ground and grow into miasma-producing plants.
The Ohmu were one of many creatures that the previous humans had created in order to purify their polluted world, in addition to the plants and other insects that live in the Sea of Corruption.
Nausicaä encounters an Ohmu at the very outset of the story. She proves to be very good at communicating with them and can even hear their calls. Eventually, she meets a herd of Ohmu at the Acid Lakes, where she rescues a baby Ohmu. There, she is held into the air by the feelers of the Ohmu. After this, the Ohmu head south into Dorok lands. There, the Dorok have bioengineered a fungus to wipe out the Torumekian Army. The Ohmu sacrifice themselves to spread the forest.
The word "Ohmu" suggests "Oh Mu(shi)" or "King Bug"
- ↑ DE 1a pg 11 (first mention), pg 13 (first appearance)
- ↑ DE 1 pg 9 (first appearance)
- ↑ DE 1 pg 125
- ↑ DE 1 pg 11
a See Page Conversions Between Editions to convert Deluxe Edition volume 1 (DE1) to other editions