EPOW - Ecology Picture of the Week

Egg mass of caddisfly, Order Trichoptera, probably family Limnephilidae

Explanation:   At the turn of this new year, we celebrate the birth of life in a small stream in northwestern California.  This tiny mass, as big as your thumbnail, holds several hundred caddisfly eggs.  

Caddisflies are good indicators of healthy streams.  Some caddisflies are intolerant of pollution, so their presence indicates lack of pollutants.

Caddisflies are secondary producers in streams.  Different species perform ecological roles of grazers, collectors, shredders, and even predators.  A diversity of caddisfly species reflects a healthy trophic ecosystem.

Studies have shown that different species of caddisfly lay their eggs on different locations and substrates in streams.  Some like particular parts of stream riffles; some like rocks or logs; others like overhanging vegetation n the shade.  Some lay eggs above the water line, others below it.  

Acknowledgment and further identification:
     My thanks to aquatic entomologist Ken Cummins for help with the identification.  Ken noted that Limnephilidae is by far the largest family of caddisflies in North America with over 300 species.  The location of this specific egg mass, in a small stream in a redwood forest in northwestern California, suggests that this caddisfly might be a species of genus Hydatophylax, which is probably the largest caddisfly in North America, or Ecclisomyia, the larvae of which produce redwood needle cases arranged like broom sticks.   Caddisfly egg masses are simply not diagnostic.