ZachK,
Generally, the "Invertebrate Threat" associated with Butterflies are related to sessile inverts.
Generally, there is minimal butterfly predation on hermit crabs, urchins, larger shrimps (pistols, cleaners, fire/blood, saron, peps, etc), hidden/ symbiotic shrimp (sexy, anenome, etc), and snails.
Butterflies favorite invert in our reef/ marine tanks are fan/ feather duster worms. They will also eat spaghetti worms, peanut, etc.
Remember that certain Butterflies also will nip/eat/harass certain LPS/ Gorgonians.
HTH