Kid's Corner: Bugs

Aquatic Insects
Besides being important for fish, bugs (especially aquatic insects, or those bugs which live on or around the water) can be an important indication of stream or lake health. Because they are so small, many bugs are easily affected by even small amounts of pollution or disturbances in the environment. This makes it important to watch the bugs carefully--if they start to die, the fish might be soon to follow!

But sometimes, it can be just as bad of a sign if you see bugs LIVING in the water, as if you see bugs DYING. How can that be? Well, some bugs have adapted so that they only like to live in dirty or oxygen-depleted waters. If there are a lot of these bugs, then chances are, the fish aren't going to be very happy--and neither are the other kinds of BUGS!

Here are some pictures of common aquatic insects (and which ones are used as water quality indicators)!

We've divided some of the common aquatic insects into three categories: VERY SENSITIVE, SENSITIVE, and NOT SENSITIVE, so that you can look for indications of stream health in your area!

VERY SENSITIVE to pollution
(Insect Illustrations by Mike Simiu)

Stoneflies are found in clean, cold streams with high levels of dissolved oxygen in them. They have two long antennae, gills behind each leg (to breathe with), two long hair-like tails, and two hooks on the end of each leg to hold on to the bottom even in the swift water. Stoneflies usually develop in the stream for 3 months-3 years, depending on the species (and there are about 500 different species just in North America!). They eat bacteria and fungi from rotting debris on the stream bottom, or they can eat other bugs, if they can catch them!

Riffle Beetle larva can be classified as SENSITIVE, but the adults are VERY SENSITIVE. This is because they have been subjected to the water conditions for a longer period than the larva (or young). The larva don't look very much like the adults--in fact they almost look like long caterpillars! But the adults have small oval bodies, and are very small, reaching only about 1/4 inches long!

Mayflies usually live on exposed rock surfaces in fast clean streams, or they might even live buried in soft stream beds for protection. They can stay in the streams for a length as short as 2 weeks or as long as 2 years, depending on the species (there are almost 700 species of mayflies in North America!) Mayflies are a common food for fish, because large numbers of flying adults often emerge from the stream at the same time.

Caddisfly larva are interesting bugs, because they make their own homes. There are TONS of different kinds of caddisflies, and each kind makes a different house for themselves out of different building materials, from small rocks, to sticks, to mud. These "tube-homes" offer the caddisflies protection and camouflage, and are sometimes used to help them catch their food. Caddisflies eat algae and small aquatic animals.

Water Pennies (can you guess how they got that name from looking at the picture?) live in cold, fast-moving streams. They eat algae and so they are often found on smooth rocks. Their own smooth, flattened bodies, allow them to resist the pull of the current and stay on the rocks. Because of the way their body is shaped, you can't see their head or legs from above, but they're tucked in there!

SENSITIVE to pollution
(Insect Illustrations by Mike Simiu)

Alderflies are carnivorous (meaning that they eat meat and actively hunt their food) and have large chewing pinchers in their mouths, so watch out--they might bite! Alderfly larva stay in the water between 1 and 3 years, depending on the specific species. Alderflies have a smooth underside and a single, straight, feathery tail.

Riffle Beetle Larva (see the Riffle Beetle Adult under VERY SENSITIVE) are not as sensitive to pollution as the adults, mostly for the reason that they are not exposed to the water conditions for as long as the adults are. They walk on the bottom of streams with tiny segmented legs on the upper middle section of its body.

Crane flies are those big flies that look like big mosquitoes--long skinny legs and long skinny wings--but their larva are very different looking! A crane fly larva is almost like a fat worm. It has no legs, and its head is just a rounded extension of the round fleshy body. They can get big--up to 4 inches long! There are about 300 species of crane flies in North America and, depending on the species, they can stay in the water between 6 weeks to 5 years before they develop into that long-legged, skinny-winged fly!

Damselflies have large eyes and long spindly legs. They develop in 1 to 4 years. Their 3 fan-shaped tails, are actually gills!

Watersnipe fly larva look almost like caterpillars. They are carnivorous and can bite, even though they look soft and cushy! They are usually a greenish color.

NOT SENSITIVE to pollution
(Insect Illustrations by Mike Simiu)

Midges are found in all but the most polluted waters. They are small--up to 1/2 inch in length--and have a sort of worm-like body. There are nearly 2000 midge species in North America, the two pictured above are only two examples of how different they can look!

Black fly larva have small suckers on the end of their abdomen (main body segment), by which they are able to anchor themselves to rocks. They can then feed by filtering food from the water with their small gills. If they want to move, they drift downstream, but stay connected to their rock with silken threads that extend from the tip of their abdomen.

Leeches are also NOT SENSITIVE to pollution. There are many different kinds of leeches, and they aren't all dangerous to people. In fact, though leeches will attach to your legs to suck your blood (just like a tick or VAMPIRE!) if you are paying attention, you can see them and just pull them off, so they're really not very dangerous. In fact, some types of leeches are very HELPFUL in the medical field. Doctors use some types of leeches to help in surgeries!!

Miscellaneous Bugs
(Insect Illustrations by Mike Simiu)

These are some other aquatic bugs that you might see hanging around the water. Do you know of any others?

Have you ever tried to make a BUG COLLECTION? Do you want to collect aquatic bugs from a stream near your house to see what the water quality is? Look at the Bug Identification activity HERE!