Why do you have little green bugs on your hibiscus?

Food source, shelter and stress describe why a hibiscus has little green bugs. It is likely that the insects in question are aphids (Aphidoidea superfamily) since the latter are voracious feeders on hibiscus. Aphids leave when ladybugs (Coccinellidae family) show up or with horticultural oil against their eggs and insecticidal soap against all other life stages.