One day in advance: make flies. Tint 1/4 oz. fondant light gray; knead in a pinch of Gum-Tex. Roll out gray fondant 1/16 in. thick. Cut out two hearts per fly using the smallest heart Cut-Out. Overlap points 1/4 in. and attach with fondant adhesive.
For bodies, use remaining black fondant. Mold into a log, 1/2 in. long x 1/4 in. wide. Attach to wings with fondant adhesive. Let dry on cornstarch-covered, smallest curve wave former.