The level 4 Druid spell "Giant Insect" reads, in part:
You transform [some arthropods] into giant versions of their natural forms... A centipede becomes a giant centipede [etc.].
Each creature obeys your verbal commands, and in combat, they act on your turn each round...
Do the giant bugs attack immediately?
The Rules-As-Written make me think, "Yes". The hobgoblin that was queued to go next in initiative order will just have to wait while this giant centipede chews his leg off.
The spell description is not explicit on this detail, though.
Here's the problem: A round is six seconds (ah, how things have changed since first edition!), and it's understood that I'm using a sizable chunk of those six seconds when a spell's casting time is "One Action". When the wizard casts "Fireball", the hobgoblins cook at the END of the casting, not the beginning. Surely the giant insects don't appear until their turn (my turn) is over?
I can think of three possible interpretations:
- The insects get their full turn immediately because it's a game, and this is just a competitive advantage "Giant Insect" has over "Conjure Woodland Creatures" or "Conjure Minor Elementals" (both level 4 druid spells).
- The insects get their full turn because it's MAGIC! The insects retroactively appear and attack when the druid starts his or her turn, or maybe they grow with their stingers already driving toward their victims' torsos. We're already violating the laws of physics with magic; a few seconds of time travel isn't something to get choked up about.
- The insects appear at the end of the druid's turn and have to wait until the druid's next turn before they can eat the hobgoblin. Again, magic violates the laws of physics, but since the rules don't explicitly say when the physics-defying bugs get to attack, we only let them attack when the laws of physics say they should.