Answer: There's a little green caterpillar that sometimes attacks bougainvilleas and consumes the leaves in a hurry. I suspect what you are seeing is frass - bug poop - especially since you are seeing them on the soil as well as on the leaves. The botanical Bt (bacillus thuringensis) which is sold as Dipel and Thuricide will control the caterpillars. Be sure to apply according to label directions. Good luck with your garden!
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