He's thinking about moths and butterflies, and how they radically change shape as they grow, from little wormy, caterpillar critters to airborne beauties.
The inside airborne contamination was caused by a change in air pressure inside the containment building that dislodged small irradiated particles in the reactor piping system.
After the vehicle became airborne, an uncontrollable roll and pitch-coupled oscillation started that forced each of the three wheels into the ground in turn.
