We seem to have an infestation of roly-polies, but I don't think they are responsible. The sparrows, who have almost taken over the yard are probably not the culprits (wish they'd start feasting on the rolly-pollies). So, that leaves the squirrels. Do squirrels eat lettuce?! Thank goodness they've left my tomatoes and peppers alone...and my swiss chard. There would be a price to pay if the critters messed with my swiss chard!!