Flower Crab Spiders and Camouflage

An unlimited number of features in the world around us speak of God’s design and wisdom. Consider flower crab spiders with the scientific name Misumena vatia. They earn the “crab” name because they resemble crabs and can walk forward, backward, and even sideways like crabs. Their two front legs are longer and extend out for grabbing prey, which they immobilize by injecting venom. Misumena vatia spiders don’t build webs to catch prey. Instead, they sit on a flower and capture incoming prey with their legs.

Another unique feature of these flower crab spiders is they can change color. The females, which are much larger than the males, have the options of white, yellow, or pale green. White is the baseline color. If they eat colorful prey, they can temporarily take on the prey’s color. For example, their abdomens will turn pink after a meal of red-eyed fruit flies. More commonly, if they sit on a yellow flower, they can secrete a yellow fluid into their outer body cells to give them a yellow color. Unlike chameleons that can change color in seconds, it takes days for Misumena vatia spiders to change their color.

When these spiders sit on yellow flowers, they are difficult for humans to see. However, they become highly visible to humans when they are white and perched for hunting on pink or red flowers. On the other hand, the arthropods that are both predators and prey for flower crab spiders have vision tuned for ultraviolet and blues. To them, the red in the flowers and the white of the spider appear dark to provide camouflage.

Flower crab spiders fill a unique ecological niche. They provide balance for the many life forms that feed on spiders and for the pollinators and plants. God has given us a diverse and beautiful natural world. Unfortunately, we take all this for granted, but when we look carefully, we see design in living things.

— John N. Clayton © 2022

Reference: The Spokane, Washington, Spokesman-Review for July 13, 2022, page A01, and Wikipedia.