Small clear inchworms?

[Royal]

Anybody ever have issues with caterpillars or small clear worms? I've found a few of these munching on some seedlings (in sphag). Looked like a snail trail, but some digging uncovered a little worm thing, about 1/4 inch long, clear with a black head. Devastated some seedlings. I also noticed a little webbing on a 'blasted' bud and investigated. Turns out this thing was just hanging out in there - eating on the unopened flower from the inside out! Maybe that's why last weeks spraying didn't kill it. I killed it the old fashioned way.

Anybody deal with these nasty beasts? How?