August in the wonderful Sierra Nevada, I'm again working with researchers who are studying stream life and water in these critical landscapes. While stopping to write beside Line Creek above Huntington Lake, I notice carefully positioned clusters: the empty pupae skins of net-winged midges (Blephariceridae - good life-cycle summary; then scroll down to the plates).
Late summer stream levels left the shells exposed, but the scoop in the rock tells how they choose a spot sheltered from the flow. Metamorphosing into adults, they would have emerged, fully-winged, under water.
Boca Reservoir, about mid-day in late July. Naturally variable flows in the Sierra have been harnessed for flushing timber to mills, irrigating crops, providing year-round potable water to cities, and keeping the river within what historically has been its floodplain, now prime locations for river-view houses. Multiple reservoirs within the Truckee watershed store and release its waters - I visited four of them, including Lake Tahoe, while staying at Sagehen Creek Field Station in July. (See my December post for more on this system, or Leah Wilds excellent Water Politics in Northern Nevada.) As the timing and volume of precipitation changes, management and expectations based on needs and weather of the last hundred years will also require some adjustment.
Stoneflies make a partial metamorphosis underwater, then crawl above the waterline onto a rock or branch, split their exoskeleton along the back and head, and slip out as adults.
The bugs are so fascinating, nearly unbelievable sometimes. Black flies live most of their lives as larvae underwater. They attach themselves to rock or submerged wood at one end and spin a net at the other to filter food from passing currents. Metamorphosing into adults, they'll pop to the surface with a little bubble of air.
What profound completion is expressed by stream invertebrates as they move between forms and environments - as if maturity requires the whole range of clinging, crawling and flying, breathing underwater and in air, appetites and risks within wholly different kinds of neighborhoods.
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