Male-specific structures on the wings of the gulf fritillary butterfly, Agraulis vanillae (Nymphalidae)

Males of the Gulf Fritillary butterfly, Agraulis canillae Linnaeus (Nymphalidae), have distinctive structures on certain veins of the dorsal wing surface that appear to be involved in pheromone production. Here we confirm and extend an earlier description of these structures. Observations using light and scanning electron microscopy indicate that in these structures, patches of several scale types alternate with scaleless areas along the veins. Some of these open areas have pores that we suggest might be the route by which the pheromone moves from cells in the wing integument onto brush-bearing scales from which it is disseminated during courtship. We have also found that although the dimensions of the basic units of these structures on the veins are not correlated with body size, larger males do have greater total vein length devoted to these structures. These findings are discussed in light of the courtship of this species and the potential for these structures to be involved in mate choice and to be a product of sexual selection.