We understand the superhero "no capes" rule—but what about shields?

Many insects know the power of this form of stylish protection. For instance, caddisfly larvae, which sometimes measure only a tenth of an inch long, may be the world’s tiniest artisans.

These aquatic insects, found worldwide, excrete a sticky silk from their mouths and use it to build a hard case from objects in their habitat, which includes stones, leaves, and shells.

The materials and shapes vary according to species and their body shapes, says Kate Boersma, an entomologist at the University of San Diego. (Read why insects rule the world.)

Some make flat, long tubes “that look like sleeping bags, and some make spiral cases that look like