Wildlife Survey & Photo Service
Hydropsyche, also called the "Spotted Sedge," are a major source of food for trout and other fish. They are extremely common in tail-water fisheries. The specimens show at the left were collected in the same sample which shows that variety of sizes in the creek at the same time. They were collected in Putah Creek. Note the scale as the larger specimen is about one inch in length.
There are many other species that resemble Hydropsyche. They are commonly confused them with Rhyacophila "Green Rock Worms" which do not have the large number of gills found on Hydropysche.
Hydropsyche larvae are real meaty - a great meal for trout. They do not build cases until they are ready to pupate. Trout can easily dislodge the larvae by rooting between rocks where Hydropsyche build their nets. See the nets a the next tab.
Hydropsyche Larval Nets
The larvae build nets that face upstream. They hide near the narrow part of the net and recover bits of detritus and other food particles from the net. You can easily see the nets in shallow water. Some areas will have hundreds of nets per square meter.
Image on left shows a pupal case glued to a rock. The shot on the right shows the same pupal case after removal from the rock. You can see the developing pupa in the case.
An "emerger" is the adult stage which has the pupal case and pupal sheath, moved to the water surface. This is a highly vulnerable period as the emergers are subject to feeding trout. At the surface, the adult leaves the water to search for mates. Hydropsyche emergers are sought by feeding trout as they hit the water surface.
Adult "Spotted Sedge" are large bugs. We have caught adult females in Putah Creek when they dive back into the water to lay eggs. In my experience they go back in the water at dusk or even as late as Midnight. We have captured many adults - in the water - during the 10:00 PM to 11:00PM sample time.
Please return for a suggested Hydropsyche pattern.
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