When checking out some squash bugs on zucchini plants, I noticed a couple of mating signal flies (Rivellia sp., Platystomatidae). These insects get their name from their tendency to wave their wings as if signaling. The two shown here weren’t exhibiting that behavior while mating.
In some species of Rivellia, the males feed the females small blobs of liquid while mating (Koethe and Van Duyn 1989). I assume this is a way of appeasing the female so the male can complete insemination.
The larvae of some species feed on the root nodules of legume plants (family Fabaceae) (Bibro and Foote 1986). These nodules are created by Rhizobium bacteria that form symbiotic relationships with the plants. The bacteria engage in nitrogen fixation, converting atmospheric nitrogen to ammonia that the plants use. When signal fly larvae damage these root nodules they can adversely affect the growth of the plants. Normally the larvae feed on wild legumes, but in recent decades they have shifted towards feeding on cultivated legumes like soybeans (Glycine max) (Bibro and Foote 1986).
Bibro, C.M. and B.A. Foote. 1986. Larval Description of Rivellia pallida (Diptera: Platystomatidae), a Consumer of the Nitrogen-Fixing Root Nodules of Hog-Peanut, Amphicarpa bracteata (Leguminosae). Proceedings of the Entomological Society of Washington 88(3):578-584.
Koethe, R.W. and J.W. Van Duyn. 1989. Soybean Nodule Fly, Rivellia quadrifasciata (Diptera: Platystomatidae): Observations on Adults Food Sources and Responses to Baits and Traps. Journal of Agricultural Entomology 6(2):83-90.