Tuesday, December 21, 2010
Lickinghole Creek: Uenoid Caddisflies
I saw a good number of insects in Lickinghole Creek (near Crozet) yesterday -- but it was pretty much "the usual suspects": e.g. large winter stoneflies (both Taeniopteryx and Strophopteryx -- mainly the former) and small winter stoneflies, a number of very large midges (Chironomids), a fair number of common netspinning caddisflies, and a few brushlegged mayflies. But I also saw a large number of Uenoid case-making caddisflies, and they are increasing in size from my first sighting (last week at Buck Mt. Creek).
Cases of the caddis family Uenoidae often show up in our streams in early December, when their cases can be very small (1/8"?): they look like compacted grains of sand that are stuck on a rock. They can be prolific, with 10, 12, or more cases stuck to a single rock in a stream, but they are normally only found in small to mid-size streams (10'-30' wide); I have never seen them in the main stem of the Rivanna. Their cases are made from grains of sand and small pebbles, but typically there are 3-4 larger pebbles attached to each side of the case (as in the photo above). Cases can be colorful or drab, depending on the mineral composition of the stream in which they are found. By February, they start to seal off both ends of their cases for pupation, often clustering together in large numbers -- 30-40 cases might be seen side-by-side on a rock.