This looks to be damage from something with chewing mouthparts. Likely a generalist insect like a beetle or grasshopper. There aren't any specific pests to Amaryllis that would cause damage like this.

If you are seeing severe damage to your plants, you may want to use something like a row cover to exclude the insects and keep them from feeding on your plants. If you're not seeing severe damage, it's not likely something you need to be too concerned about.