I took these photos yesterday along a trickle of a waterfall, in an amazing box canyon in the Catalina Mountains near Tucson. At the top of this waterfall I found fly larvae, living under 1/4 of an inch of flowing water. These larvae in the first two photos are blackfly larvae--all one species in the family Simuliidae. They anchored themselves to this smooth quartz rock by using silk that they spin from their abdomens. They feed as barnacles do, by sweeping in algae and other small creatures using fan-shaped structures attached near their mouths. As adults, they feed on the blood of vertebrates. In other parts of the world, they vector terrible disease agents such as nematodes that cause river blindness. At the base of the waterfall, I found a long whirligig beetle waiting to capture prey that fell onto the surface film of a tiny pool the size of a dinner plate. Remarkably, species in this family of beetle (Gyrinidae) have two sets of compound eyes--one set that sees the world above the surface film (e.g., to detect giants with cameras) and one set that sees the world below. The beetle found itself next to a large carpenter ant soldier that had fallen down the waterfall, but was too big to feed upon. Especially in this desert, water plays a major role in shaping the distribution of plants and animals. Check out these links to see a drawing of blackfly larvae, the compound eyes of a gyrinid beetle, and a story on a convergently evolved four-eyed fish!
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