When I piped yesterday's oyster, I discovered that tip #98 by Ateco is really quite versatile. As you may recall, it is scallop-shaped and grooved on one side:dusting pouch filled with a 50/50 mix of powdered sugar and cornstarch. Hold a pastry bag loaded with stiff consistency royal icing and fitted with tip #98 just above the surface of your fingertips, and start squeezing steadily. Coax the icing into curling over itself.
AmeriColor, or use a toothpick to dab on a dot of black Soft Gel Paste food color (also by AmeriColor). This little critter might be considered a pest, but I think it would be appropriate on any garden-themed cake or cupcake.