Satan's Butterfly by Shawn M. Klimek

Spanning the stems of a prickly cactus, a spiderweb glittered in the morning dew like a sequined doily. When a yellow hornet—actually, a demon—descended nearby, the web’s owner warily revealed itself.

“What now?” demanded the spider (also a demon).

“Just watch.”

Pimples like blackberry drupelets erupted all over the hornet's body. These bulged into pustules, before mushrooming into tarry lobes, like a smoker's lungs. These swelled and mutated until the mass resembled a bloated, decomposing manatee drowned in crude oil.

“Strange,” gurgled the transfigured hornet.

“Don’t tell me! Satan said you'd become a butterfly—and you believed him?”