Where do insects go when it rains? Large insects such as butterflies often perch in sheltered areas out of the rain. Rain can be a mortality factor for butterflies. What about smaller insects such as mosquitoes?
Dickerson and colleagues, writing in PNAS describe observations of mosquitoes in a flight chamber colliding with water droplets. Their study (and video below) offer insights into insect adaptation to rain. Mosquito wings have very low mass and are flexible. When hit by a raindrop, the wing bends to absorb some of the impact. The raindrop will bounce like a tennis ball hitting a racket.
At higher speeds, raindrops hitting the wings will knock the mosquito about. However, mosquitoes rapidly recover from the blow and continue their flight. Mosquitoes suffering a direct hit can lose altitude, and be trapped by the droplet. However, the water is quickly shed and the mosquito emerges laterally and continues its flight. Unless mosquitoes are flying too low to the ground, they will emerge from the rain drop before it slams into the ground.
The outside of insects is water repellent, primarily to prevent dehydration from evaporation of internal water from the insect. The water repellency also sheds water and keeps the insect from getting “soaked” even in the middle of a rain storm.
