Collected April 24, 2010, in Santa Clara County, California, near Milpitas, by DNelson. 10S612687E, 4142253N (WGS84 datum), elevation 728, in an intermittent spring and seep named the Rope Swing Spring that flows only about 30 feet, five months of the year.
View up the Rope Swing Spring and seep. The water comes out of the ground just at the upper end of the muddy area.
The seep is less than a half-inch deep and only about two feet wide. It flows into the ground within 30 feet of coming out of the spring. The nymphs are about 5-8 mm in size, some of them pre-emergent (note dark wingpads on the second nymph photo). Some were undergoing ecdysis on the day after being collected, but died before emerging.
Dorsal and volar view of nymph. Note branched thoracic gills.
The gills appear to be coming from two areas on each side of the anterior thorax.
Adults were collected in the immediate area (within 2 feet of where the nymphs were collected).