The smaLL BLck bugs are aphids and they're very common on hibiscus and the sticky residue is honey dew.. The ants are "milking" the aphids to get the honey dew so you will normally see both insects at a time. If you want to be organic you can simply rinse the plant off and remove them both and you can also add 1TBSP of dish detergent to a spray bottle of water and spray the plant real well, especially under the leaves and it will suffocate the aphids. If you purchase an insecticidal soap, it will also work. Try not to use any insecticides as they will kill the beneficial insects and lady bugs LOVE aphids..Good luck