Squiggler

A Squiggler is a miniature Wiggler that appears in New Super Mario Bros.

With three body segments and a head about twice the size as the other segments with a sprout on it's head, this tiny Wiggler crawls around the perimeter of pipes. Squigglers are only seen in World 7-A and are obviously the baby versions of the Wigglers. It can be inferred that they are born in pipes. When they mature enough they (presumably) become a Wiggler, then a Flutter.

They also reappeared at Mario & Luigi: Bowser's Inside Story, this time with a more vivid color.