“Sensitive” Macroinvertebrates
A stonefly larvae. These animals have two tails and are only suited for highly oxygenated environments, making them great indicators for a healthy stream! 
A mayfly larvae. The feathery looking appendages on the abdomen of the larvae are actually its gills! They require highly oxygenated water with little pollutants, making them a great indicator for a healthy stream! 
A casemaker caddisfy. These animals take substrate material and create a little home from it that they can hide in! They can use rocks, leaves, anything they can get their claws on to make their homes. 
A riffle beetle. This animal prefers a flowing stream with a nice amount of rocks and riffles in order to hunt for algae and other material. They don’t like stagnant streams very much at all. 
A gilled snail. Unlike other snails, this species is able to breathe underwater thanks to its gills! This means that it needs a supply of clean water to not clog them up.
All of the organisms you see above are listed as “sensitive” species. This means that they can’t take much pollution, and are indicators of a healthy stream.
“Less Sensitive” Macroinvertebrates
A hellgrammite (or dobsonfly). This is a predator species that lives in streams. Those large jaws on the front of it allow it to capture prey with relative ease! 
A scud. These animals are amphipods, meaning that they lack a hard shell like shrimp. They are also commonly known as “side-swimmers” because of their tendency to swim on their side. 
A crane fly larvae. These worm-like animals are very important to an ecosystem, as they eat detritus on the bottom of the streams and help break it down. They also serve as a tasty snack for other animals! 
A damselfly larvae. Those three tails at the end of the animal are actually their gills, which allow them to breathe underwater. 
A dragonfly larvae. These animals are large predators, getting big enough to actually hunt tadpoles and small fish before leaving the water as adults. 
A crayfish. Related to the crab and lobster, this freshwater version lives on the bottom of streams and enjoys eating what bits of matter it can find. 
An aquatic sowbug. Related to the pillbugs on land, these animals eat decaying and dead plant matter on the bottom of streams, helping keep the stream healthy! 
A net-spinning caddisfly. These animals are able to make a little silken net to catch its prey.
These organisms are known as “less sensitive” species. Much like the “sensitive” species, the macroinvertebrates listed here indicate stream health. However, these species can take more pollution and a lower stream health than the sensitive species. Finding these species doesn’t mean that your stream isn’t healthy, but it does show that the quality could be better!
“Tolerant” Macroinvertebrates
A freshwater leech. Like most leeches, this animal sucks the blood of other animals. However, it is an important food source for other animals. 
A lunged snail. This species of snail cannot breathe in water and have to crawl up towards the surface in order to get air. 
A midge fly larvae. They don’t require much in the way of stream health and are a very important food source for a lot of stream predators. 
A black fly larvae. These larvae are an important food source for stream predators. 
An aquatic worm. These animals eat detritus on the bottom of the stream and serve as an important food source for larger predators.
These macroinvertebrates are generally found in streams that have a poor quality, either with a lot of pollutants or a lot of sedimentation. If you only find these during your survey, your stream is probably not doing well healthwise.
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