Answer: A number of moths overwinter in one form or another in leaf litter or soil but based on your description it sounds rather like the garden webworm caterpillar (Achyra rantalis). This pest can have two to four generations a year and overwinters as pupae in the soil (the larvae also drop to the ground when disturbed), so I suppose it is possible. For a good close-up photo of this and other common garden insects in various life stages you might "enjoy" a look at Rodale's Color Handbook of Garden Insects by Anna Carr, paperback ISBN 0-87857-460-3. You could also see if I've guessed right!
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