well maybe my dm made a mistake on how big these worms are. i got the impresion that they were rot grub size,not earth worm size, am i wrong, and if they are green they wouldn't be that hard to see especialy if you have someone trying to brush it off and saying get it off me. in regards to magic missle doing damage to charactors the worm is on, in the spell descrip it says the missle can only strike one creature.