FOREWORD 



"Aquatic Dryopoid Beetles (Coleoptera) of the United States" 

 is the sixth of a series of identification manuals for se- 

 lected taxa of invertebrates occurring in freshwater systems. 

 These documents, prepared by the Oceanography and Limnology 

 Program, Smithsonian Institution for the Environmental Pro- 

 tection Agency, will contribute toward improving the quality 

 of the data upon which environmental decisions are based. 



Additional manuals will include, but not necessarily be lim- 

 ited to, freshwater representatives of the following groups: 

 branchiuran crustaceans [Argulus) , amphipod crustaceans 

 (Gammaridae) , isopod crustaceans (Asellidae), decapod cray- 

 fish crustaceans (Astacidae) , leeches (Hirudinea) , polychaete 

 worms (Polychaeta) , freshwater planarians (Turbellaria) , and 

 freshwater clams (Sphaeriacea) . 



Ill 



