Note the small yellowish head and single proleg on the left. With most aquatic insects only the immature stages are aquatic and the adults are terrestrial or capable of flight. Adult beetles, however, are often as common in streams as are the larvae. Photo courtesy of Lara Panayotoff. Photo courtesy of Lara Panayotoff.
Adults are terrestrial.
Note the large head and jaws and lateral filaments on abdomen. Photo courtesy of George Folkerts. After collection, the samples are examined either in the field or in the laboratory. The invertebrates are removed from stones and organic debris, identified as belonging to a particular taxonomic group, and counted. Once counted, invertebrates can be compared to samples taken in the same stream but at different times, such as before and after a suspected pollutant has entered a stream.