Below are links to photos and distribution maps of aquatic macroinvertebrates found in Iowa. The vast majority were collected from rivers/streams during stream assessments that UHL/IDNR conducted across the state since about 1994. The information provided is certainly not complete and may not include studies conducted by other individuals or agencies, though we tried to summarize all the published collection records we could locate. When viewing distributional maps please consider:

• Some areas of the state have not been sampled, just by chance. For example, while creating the maps it was apparent that we had no sampling sites (and therefore no collection records) from Humboldt County.
• We have not sampled many of the state's lentic (standing water) habitats like lakes, pond and wetlands. There are likely dozens of species that prefer these habitats but we have not encountered them in streams.
• Some species show definite geographic affinities, for example being only found in the northeast corner of the state. More widespread species often display a "checkerboard" pattern of distribution across the state, and it can be assumed (usually) that they occur statewide.
• Stream assessments were usually conducted between mid-July and early October. Some groups of aquatic insects will not be encountered during this time due to the timing of their life cycles. For example, some exist in a dormant egg stage during the summer, hatching in the fall and developing to adults by late winter or spring. Species with this type of cycle may be quite common and widespread, but will be under-represented by our collections.

Providing maps and photos of all of Iowa's aquatic macroinvertebrates is more than we can handle so we have concentrated on the aquatic insects. Whole groups like freshwater mussels ("clams") which we did not encounter frequently are not presented. Some information is provided for custaceans (crayfish, scuds, aquatic sowbugs), water mites, snails and leeches. The aquatic insects are divided into the main groups (orders) below. Use this on-line key created by the University of Minnesota if you need help determining the order or family of aquatic insect you are interested in.