The oldest architect in the world: the trichopter. Here are architects and not the least. Builders of the effort, builders against the current, the trichoptères have been in the waterfall wave for two hundred and fifty million years. They built gravel towers long before our births and our claims. They wove particle traps in gravel arches whose meshes have constant dimensions to the nearest micrometer. The capsules of the Trichopterans sheaths all have the same weight. Their sleeves are examples of cutting-edge technology, their interiors lined with sticky protein silk form a perfect cone. Water circulates in the case irrigating the gills and the integuments of the insect. The role of the holster in breathing is as important as the protective role. The case is adjusted with each molt of the insect. It is profiled to defend it, allowing it a perfect metabolism during the nutritional activities of the larva and its transformation into a nymph. The larvae filter and clean the water column of the rivers and recycle the material from the sediments. Larvae grow underwater in one year over five stages using four moults. The larva fixes its sheath to a support, seals its opening with silk and then turns into a nymph. The insect remains active to ensure its oxygen supply throughout the pupal stage, which lasts about three weeks in most species. Before going to the adult stage, the nymph leaves her shelter by cutting an opening in the silk with her mandibles. Once out of the scabbard, it swims to the surface with its furry hind legs and a head methane bubble to soar into a new world. More intestines, priority to reproduction, the insects find their partners in a few days. This butterfly, whose larva and nymph are aquatic, becomes aerial adults because it has less predator in the air than in water.