Conversion

The freshly assembled caterpillar chewed a twist of rebar and dug shiny divots in the ragged end of steel. Its hunger was no less urgent for being programmed, so it ate and expelled the component iron and carbon until its thremostat forced a rest. As the caterpillar bled its waste heat, it heard a delicate clockwork flutter. 

A butterfly landed on broken concrete. Wings of stained glass and titanium absorbed the sun and powered the telescoping proboscis tipped with hydrochloric acid. It dissolved a thimbleful of concrete, lapped up the slurry, and flew away. It was impossibly lovely.

The caterpillar ignored its returning hunger and watched the butterfly dance while it contemplated existence. Its creators had given it sufficient processors to know that, unlike a real caterpillar, its form was fixed and it would never be anything more. It didn't know why this understanding was included. Cruelty, indifference, or challenge were all equally likely. The creators were inscrutable. 

In the time that it took the butterfly to land on another rubble pile, the caterpillar decided it had no obligation to the role it was designed to perform.

The caterpillar used a receiver imbedded in its thorax to access the accumulated knowledge of pupal metamorphosis, reconfigured its abdominal segment, and forged its iron and carbon into steel silk. It spun a cocoon to see what would happen.

Eleven meters away, perched on the limestone sill of a burned out brick tenement, an aluminum sparrow cocked its head.