[LMB] plague worms

[adkinslawfirm at mindspring.com]

Our Gwynne delightfully wonders, "Ok, here's the interesting question: it's become fashionable for teens to deliberately host a worm to make interesting designs on their bodies - how do they direct the worms into the patterns they want?"
 
Probably heat or cold near or on the skin.  Something as simple as an ice cube or a candle might do the trick, although I imagine they've figured out something more precise and sophisticated.
 
Jerrie