Don't know exactly where it was in before it crawled out into full view. I found it while pulling weeds from around my gooseberry plants (Ribes uva-crispa) with lawn, near honeyberry shrubs and mulching with wood chips. Weeds were: grasses, plantain, ground ivy, rudbeckia "goldsturm" etc. The wood chips had been in a huge pile for 6 months. It crawled up onto my compostable paper leaf bag. I searched ALL caterpillar photos I could in Bugguide, some are close, like armyworm, striped garden caterpillar, etc.. but this one has a yellow CENTRAL dorsal line and a BLACK head. Strangely, its' pattern is almost IDENTICAL to a garter snake's, as well as its posture (see photo comparison included, photo credit http://www.naturenorth.com/Herps/images/Red-sided_04.jpg). Then it has me wondering if it is not a caterpillar but a fly larvae. I let it go after photographing it, having no clue it would be so hard to identify, given its' bold colors. I did not measure it when I photographed it so it may be a bit smaller or bigger.