14 Apr

The Wet, Wondrous, and Wild World of the

Caddisfly

During the warmth of a late summer night in any of our 50 states, if you take an evening stroll along a river trail you will find thousands of winged companions. Mosquitos will definitely be in the mix, but if you look closely you’ll see a wonder of the insect world. These small, moth-like insects come out at dusk, often clouding around lights. They emerge by the millions and can only be found near lakes, rivers, and streams. They’re on a two-week mission to find a mate, copulate and lay eggs before they die. Their mission is so important that the adults don’t eat.

The Wet

Meet the Caddisfly. It is closely related to butterflies, but its lifecycle is drastically different. Unlike a butterfly, whose larval form wanders around on leaves, the caddisfly spends most of its life underwater. That’s right, underwater; and they never have to surface for air. Caddisfly larvae have gills. They breathe dissolved oxygen much like a fish. When the larval stage ends, they shed their gills and the adult will breathe air.

The Wondrous

The transition from water to air is not the only thing that makes caddisflies a wonder of the insect world. They also build their own homes. When we think of insect builders, wasps and bees come to mind with their great communities of wax or shredded paper. The house of a caddisfly is far different. It resembles a protective sleeping bag. Like caterpillars, caddisfly larvae can produce silk. The larva gathers small twigs, rocks or sand and uses the silk to bind it all together. Their lower body is soft and the newly formed conglomerate covering will protect the larva from predators. A caddisfly will use whatever is available. In laboratory studies, larvae were given tiny glass beads and precious gems. It didn’t take long for the insects to create little cases of sparkling beauty.

Caddisfly in the Wild

Caddisfly copy

Caddisfly jewelry in the lab

CadisflyJewelry copy

The Wild

The third marvel might not be as pretty, but to a scientist it is radiant. In the field of water biology, caddisflys are regarded as an indicator species. They received that classification due to their high sensitivity to pollution. Caddisfly larvae require clean water with high, stable levels of dissolved oxygen. Small amounts of contamination can cause an entire population to crash. Finding their presence in the water column enables water scientists to conclude that a stream is healthy.

If you run out to the nearest stream, begin turning over rocks, and don’t find any caddisflies don’t worry. If you can’t find a caddisfly it doesn’t necessarily signify bad water but it does raise questions. Perhaps it was a drought year, or the stream lacks the necessary food; there could be a variety of factors. The indicator message is that the presence of caddisflies always suggests clean water, but their absence doesn’t always mean it’s polluted.
Though they spend most of their lives below water, out of sight, caddisflies are one of the wonders of the insect world. From their small one caterpillar condos, to their ability in determining if water is clean, caddisflies are definitely wet, wondrous, and wild.

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