This species is part of the first category of macroinvertebrates that can be used to indicate water quality. Mayflies lay their eggs in water where the nymph form will eat decaying plants and algae. (A nymph is a young insect that greatly resembles the adult form that it will grow into. This can be compared to larvae which will go through a complete metamorphosis like a caterpillar turning into a butterfly.) The nymph will go through several stages of molting until it resembles an adult Mayfly with wings. At this stage, the Mayfly will live out of the water. Mayflies can be identified by their 3 long tails and the nymph, in particular, by its gills on the sides of its abdomen. These insects cannot tolerate polluted water so you will know that you have quality water if you can find them living in it.
Crayfish are part of the next category of macroinvertebrates. They are not as sensitive to pollution as Water Penny Beetles and Mayflies, but they cannot live in heavily polluted waters. This creature has multiple names: crayfish, crawfish, crawdad. It looks slightly similar to lobsters, but crayfish are much smaller and exist primarily in freshwater, particularly creeks. They hide under rocks and eat a variety of things, such as snails, insects, worms, and vegetation. Crayfish have large front claws used for attracting mates, fighting, and grabbing food. The other 4 pairs of appendages are much smaller and used for walking, swimming, and circulating water for breathing. Very interestingly, some species of crayfish live up to 20 years.
This insect belongs to the third and final category of macroinvertebrates that indicate water quality. The Rat-tailed Maggot thrives in stagnant and polluted water so their presence indicates poor water quality. How this insect is able to survive in polluted and bacteria-filled water when most other insects would die is very interesting. The Rat-tailed Maggot is covered with very small spikes called nanopillars. These spikes prevent bacteria from touching the body of the maggot similar to a porcupine. Another feature that allows these maggots to thrive is their long syringe-like tail. These tails can be pushed through the water’s surface and allow the maggot to breathe. Breathing in the air instead of water saves the maggot from low oxygen levels due to eutrophication. While these maggots may look nasty to some people, they are very harmless and do not sting, bite, or carry disease. Furthermore, after metamorphosis, the maggot becomes an adult drone fly that resembles a honey bee. Similarly to honey bees, the drone fly is a great pollinator, particularly to some vegetables found in gardens.
Craneflies are in the same category as crayfish regarding how they handle polluted water. Like the Water Penny Beetle, these insects undergo full metamorphosis. They start their life-cycle hatching from eggs in water or in the soil near water. As larvae, craneflies resemble worms since they have no appendages. They eat fallen leaves primarily, so this stage of life for the cranefly happens mostly in fall and winter. As spring and summer approach, the larvae burrow into stream beds. Cranefly larvae have 4 stages of development and, after their final stage, they move out of the water to pupate. Then, it takes 1-2 weeks for the pupa to develop into an adult Cranefly. Adult Craneflies do not live very long, only long enough to reproduce. An interesting thing about Craneflies is they are considered to be the worst fliers of any species that can fly.
This beetle is very unique and interesting. The larval form is small and round with nothing but a shell that is visible. The underside reveals 6 legs, a small head, and gills at the bottom. The larval form of these beetles uses their clawed legs to cling to the underside of rocks where they feed on algae and moss. These beetles need highly oxygenated water which makes them sensitive to eutrophication, a process where oxygen levels drop as algae grows in excess to the point of constant plant matter decay. . Similar to the Mayfly, these beetles are an indicator of good water quality; however, Water Penny Beetles tend to live in fast-moving water so their absence in certain waterbodies is not necessarily an indicator of bad water quality. When these beetles grow into their adult form, they more closely resemble a typical beetle with a blackish shell and visible antennae. Some adult Water Penny Beetles are air-breathers and can be found outside of water, while others will remain aquatic for their whole life. An interesting fact about Water Penny Beetles is that the adult form only lives for a couple of weeks so it is possible that they may not eat at all after metamorphosis.