Why do tree roaches try (and occasionally succeed) to come into the house after it has rained several days in a row? They even mention it on the local news. I hate those suckers with a passion! Does their food get washed away? Is their home flooded?
American cockroaches fly to search for food an mates. However they are quite prone to dying from drying out, which is why they live in moist environments and only active at night. A large part of their defence against drying are waterproof the wing covers which shield their abdomen from dry air. So needless to say, when they fly they dry out even faster.
As a result, they will only fly when the humidity is high, which usually means after rain in a lot of areas. In the tropics, they tend to be active throughout the wet season regardless of whether it has recently rained.
Is this why boric acid is a good defense, as it appears that would dry them out?
It does according to the story I’ve heard; it scratches their cuticle, leading to desiccation.