As their name suggests, predaceous diving beetles are capable predators both in their larval and adult stages, feeding on aquatic invertebrates like mosquito larvae; with larger species dispatching small vertebrates (tadpoles, salamanders, small fish). Adults are excellent swimmers. Their streamlined, oval bodies are equipped with flattened hindlegs, which they use to row in unison, like oars. While adult beetles spend much of their time in or under water, they still need to breathe air. They either stay toward the surface with the tip of their abdomen sticking just above the water or can trap a bubble of air between their wings and abdomen, essentially creating a “scuba tank” that will let them stay under for long periods of time. Rhantus consimilis is less than half an inch long and found in warm, weedy grassland ponds, both permanent and vernal, across southern Canada and the northern US, and in the west, south to California.
Photo by: Glenn Marangelo on 5/1/21 in Clinton, MT