Most fly fishers have likely seen adult caddiflies skittering on the surface as they drop their eggs and allow them to sink to the bottom. Some caddisflies, however, take a more active role in placing their eggs where they are more likely to be safe from scavengers and are more likely to hatch. This video shows adult caddisflies crawling underwater to lay their eggs on the underside of a rock. As they penetrate the surface, they trap air under their wings. This air bubble will sustain them for the 5-15 minutes needed to lay their eggs. Once they have laid their eggs they will sometimes crawl back to the surface and fly away, but many will simply release their hold and drift away with the current. At times, there will be thousands of adult caddisflies in the drift. This is why wet flies can be so effective in the days following a caddisfly hatch.