This tiny instar Black Swallowtail Caterpillar sensed danger when I was moving its leaf for a better shot. The orange antenna on its head popped up. This is an organ called osmeterium. It emits a foul smelling odor when the caterpillar feels it's in danger. This one was so small, I didn't smell anything. I have smelled a mature caterpillar and it is stinky!
