by Crystal Cockman
October 21, 2015
Misumenoides formosipes, the Whitebanded Crab Spider. Photo by Ann Piehl.
With the arrival of fall, one of the most abundant wildflowers around is the beautiful yellow goldenrod. They are also one of the favorite hunting grounds of the unique crab spider (Misumena vatia), which are even sometimes called the goldenrod crab spider. Although crab spiders occur all across the world, the species Misumena vatia is a Holarctic species, meaning it is found all across the northern hemisphere. Crab spiders are also the most abundant of flower spiders.
They are named crab spiders because that is what they look like – a crab, with a wide and flat body, and the first two pairs of legs are larger than the rest and they keep them spread open for catching prey. Like crabs, they can walk sideways, as well as forwards and backwards.
These spiders can be white or yellow depending on the color of the flower in which they are hunting. They also have a unique ability to change color by secreting a yellow pigment into the outer cell of their bodies. The yellow pigment can also be excreted and removed if the spider spends time on a white plant. The change from white to yellow can take up to 25 days and the change from yellow to white about 6 days.
Goldenrods attract a lot of insects upon which the crab spider can easily prey. The camouflage of the spider means that it can expend more energy on reproduction because it does not have to spend energy finding food or escaping from predators.
To catch their prey, they sit on the flower and wait for it to pass by and they grab it and inject venom. Unlike other spiders they do not wrap their prey with silk but instead hold onto them while they suck their fluids. Because they have venom, they are able to eat invertebrates larger than themselves, including butterflies, bees, and wasps. Their bite is not dangerous to people though.
Crab spiders are an annual spider, which means they die out each year. Males mature earlier and mate and die, whereas females will live until they lay their eggs and guard them until cold weather. Females fold over the tip of a leaf and use a web to attach it, creating a pocket in which to lay her eggs. Milkweed is a favorite host plant. The eggs hatch approximately three weeks later and the young overwinter and mature the next spring or summer.
The next time you find yourself in a field of daisies, sunflowers or goldenrods keep your eyes out for the crab spider. They are just another example of how nature creates interesting adaptations for a creature to fit their surroundings.