Perched on a rooftop along Interstate 95 in Providence, the 58-foot-long, 9-foot-high insect could be mistaken for a prop for a horror flick, perhaps titled ‘‘The Termite That Ate Providence.’’ But the ‘‘Big Blue Bug,’’ as it’s affectionately known, is more quirky mascot than ominous threat. The two-ton sculpture of reinforced steel and fiberglass was erected on the roof of New England Pest Control in 1980 and quickly earned a soft spot in the hearts of harried commuters and fans of the offbeat. The bug’s more formal name, ‘‘Nibbles Woodaway,’’ was the winning entry in a 1990 radio contest. While many would think that a giant blue bug needs no embellishment, the folks at NEPC deck Nibbles out in holiday finery several times a year.