Players be like
Buzzkill DM: Locusts, even under the loose control of a druid, are not intelligent enough to be "willing" to be transformed, so they can't be targeted by animal shapes, rules as written.
Better DM: That's cool as hell. Do it.
Best DM: I'll allow it, but you better start watching the skies from here on out. If you can do it, then the enemy can too.