Friday Facts

Mayflies are among the only insects that molt after gaining wings.

This is incredibly rare in the insect world. Most insects molt their final time into their winged adult form. But mayflies have a unique intermediate stage called the subimago—a winged but dull-colored and somewhat clumsy version of the adult. They then molt again into the fully mature, sexually active imago stage.

This strange two-step adulthood only lasts a day or two at most, often just hours—which adds to the mayfly's fleeting beauty and ephemeral symbolism in art and literature.

It’s like they get a trial run at flying before their final, brief performance.

Some caddisfly larvae build their cases out of silk—underwater.

That may not sound surprising—until you realize that caddisfly silk is structurally similar to spider silk, and they spin it while submerged, something only a handful of animals can do. Even more remarkable, their silk adheres to wet surfaces—rocks, sand, wood, even other insects—and works in turbulent water.

Caddis larvae use this silk to construct portable cases from surrounding materials: pebbles, twigs, snail shells, or even grains of sand, depending on the species. What’s wild is that the material chosen can reflect local conditions so closely that researchers sometimes use caddis cases as a kind of biological record of the streambed.

In short: they’re underwater architects using waterproof glue that human science still hasn’t quite replicated.

Stoneflies were among the first insects to develop wings—but they never really took off.

Fossil records show that stoneflies belong to an ancient lineage of winged insects that likely emerged over 300 million years ago, during the Carboniferous period. Despite their long evolutionary history, they’ve barely changed—making them living fossils.

Interestingly, while they have two pairs of wings, many species are clumsy fliers or barely fly at all, preferring to crawl, flutter awkwardly, or simply stay grounded. It's like they were early adopters of wings but decided flying wasn't really their thing.