Aquatic insects as biological monitors of heavy metal pollution.

A mayfly, Ephemerella grandis, and a stonefly, Pteronarcys californica, were exposed to lead, zinc, copper, and silver to determine the acute metal toxicities. The insects tested were found to be more tolerant of the heavy metals than most fish. They concentrated the metals in relative proportion to the occurrence of the metals in the stream by some predictable, reproducible factor. These data, together with field tests, indicate aquatic insects may serve as effective biological monitors of heavy metal pollution where fish-kills are involved.