A mosquito can smell the air you breathe out from 50 meters away, about half a football field. Your house is screaming "human" to every fly and mosquito in range, and they evolved to come find you. To a butterfly, the same house is silent. Flies and mosquitoes evolved to follow us around. The common housefly spread across the planet from the Middle East by trailing our garbage and farm animals. Nine out of every ten flies you see indoors are this one species. Mosquitoes lock onto the carbon dioxide in your breath. A 2015 Caltech study mapped the mechanism in detail. Your body heat, your sweat, your shower steam, your trash, all of it is what these insects evolved to track down. Butterflies went the opposite direction. They evolved to find flowers, with smell receptors tuned to flower chemistry. A kitchen full of frying bacon doesn't even register. They drink nectar through a long coiled straw called a proboscis, built for flowers and not much else you'd find in your house. The navigation problem is bigger. Most butterflies fly only during daylight hours, steering by the position of the sun. Monarchs have a tiny brain region that tracks the sun across the sky like a built-in GPS. Inside a house, the sun disappears. Indoor lighting gives them nothing to navigate by. The compass just breaks. Any butterfly that drifts indoors loses its bearings within seconds, which is why one trapped in a sunroom bashes against the windows for hours. Butterflies can't generate their own body heat. They are basically little solar panels, needing direct sunlight to warm their flight muscles to around 86 degrees Fahrenheit before takeoff. Most rooms never get that warm, which is why a butterfly indoors can barely fly. And there is nothing in your house for a butterfly to do. They only lay eggs on very specific plants, like milkweed for monarchs or thistle for painted ladies. Your couch is neither, so even a butterfly that loved your living room couldn't reproduce there. About 18,000 butterfly species share these traits. Houseflies, by contrast, are one of the most successful animal partners humans have ever had, even though nobody asked for them. The joke is right, just for the wrong reason. Butterflies skip your house because nothing in it looks like a flower in open sunshine.

@anishmoonka Evolution did us dirty. Sometimes, I seriously question evolution: “Despite all the things available in the world, how come it came to this point that mosquitoes need our blood for nutrients?” Plus, they are highly irritating creatures. x.com/pathless__path…