 The thoracic legs are reduced, but always present, and they move by rolling waves rather than walking with individual prolegs.They even use a lubricant, a kind of liquefied silk, to move.Larvae might be confused with the similarly flattened larvae of lycaenid butterflies, but those caterpillars have prolegs, are always longer than they are wide, and are always densely covered in short or long setae (hair-like bristles).