Assignment:
We will compare species composition between two lakes. The insects you have "collected" will be a mix of benthic macroinvertebrates and aquatic macroinvertebrates. Remember, aquatic macroinvertebrates indicate the health of the stream because they are permanent residents of the aquatic system and they only disperse over short distances. Since they only move short distances they are highly susceptible to pollutants in the water.
Therefore, the species present, how dense those populations are, and types of macroinvertebrates can tell us if there are problems in the aquatic system and if pollution is present. We use them to measure the health of the stream and typically long-term data on the types, density, and species of macroinvertebrates are used to indicate at what time point pollution occurred, to compare systems, etc. Here are pictures of our two lakes.