Episode 138 – Crab Spider: A Fantastic Floral Friend

“And today we’re talking about a spider that sat down beside a pretty flower, expertly showcasing a poetic light and dark juxtaposition. But more on that later.”

When your relatives have found a tried and true method of success, it may be hard to strike out on your own path in order to innovate. But innovation may lead to new interesting ways to achieve your goals. The crab spider does just that. They put on a colorful coat and venture off the beaten web. But this little arachnid faces challenges and vulnerabilities that her spider kin never encountered. Such is the nature of Life, Death, and Taxonomy. 


When it comes to shape, it looks like a spider turned a cootie catcher into its home like a hermit crab.

It has eight legs, like all spiders. But its two front legs are a lot longer and more powerful than the rest. 

It has a broad, round cephalothorax attached to a huge opisthosoma (abdomen) that has pronounced corners sticking out to make it look like a delicious pork dumpling.

It also has an angry ridge that forms a v-shaped eyebrow on top of its head. In pictures, I can see two eyes facing front and another two out in the corners of the V, but I can’t ever see the other four. That’s because they’re on the other side. According to Truly Nolen, they have 360 vision at all times.

But for color, they range widely. Some are completely white with some yellowish-brownish streaks (really solidifying the chique dumpling look) while others can be bright green, yellow, and even pink.

I read that the color is often adapted to the environment, but I can’t tell if they can change color on the fly or if certain breeds prefer certain flowers and so take on the color of those flowers through adaptation.

Measure Up

Welcome to the beloved Measure Up segment. The official listener’s favorite part of the show! The part of the show when we present the animal’s size and dimension in relatable terms through a quiz that’s fun for the whole family. It’s also the part of the show that’s introduced by you when you send in audio of yourself saying, singing, or chittering the words “measure up” into ldtaxonomy at gmail dot com. We have a very special Measure Up intro this week from Mason! 

Female Body Length

  • 6–7 millimetres (0.24–0.28 in)
  • How many female crab spiders go into the width of the world’s largest flower?
  • Hint: Rafflesia arnoldii has the largest bloom in the world. The plant grows in Indonesia, and it’s a parasitic plant. The flower attaches to a host plant and saps it of water and nutrients. 
  • 129 crab spiders. The bloom can be three feet across.

Male Body Length

  • 2–4 millimeters (0.079–0.157 in)
  • How many male crab spiders go into the length of Bulgaria’s border?
  • Hint: When talking about the length of a boarder with a coastline, you are going to run into something called the coastline paradox. For instance, several organizations measured the length of the U.S. coastlines and came up with several wildly different answers. That’s because a coastline is never straight. The closer you zoom in, the curvier each section becomes. So if you measure a coastline in miles, it will be a lot shorter than if you measure it in inches. The coastline paradox means that a coastline’s length depends on the length of the unit you use to measure it. So even if your guess is way off, it may still be right, and no matter what, it will be wrong.
  • 561,250,000. The coastline is about 2,245 kilometers (1395 miles).

Crab Spider Fast Facts

Diet: It loves to eat flower-visiting insects like butterflies, bees, and even wasps. 

Interestingly, the female never shows any aggression during or after mating

Crab Spider Range

Lives and the Palearctic region – which is the northern half of the eastern hemisphere. It lives everywhere from Portugal and most of continental Europe all the way to Japan. It also lives in some places in North Africa like Egypt. It likes warm, dry, grassy areas.

Major Fact: Webless Wonder

Spiders are known for their web crafting ability, but many species of crab spiders don’t build webs at all. However, they don’t have the amazing jumping abilities that jumping spiders have, so hunting down prey isn’t a great option either.

Instead, like their web-building kin, they lie in wait for their prey. But they don’t trap them, they ambush them. So where’s the best place to ambush a bug? Why a flower of course!

What are the Drawbacks?

But this method presents two problems. A flower is raised and fairly exposed to other predators that can eat the spider, like birds. It’s also a visible spot for prey to see them. The second issue is that flowers might attract some dangerous game like bees and wasps. 

The crab spider solves the first problem through camouflage, and blending into a flower means dawning some pretty brilliant colors. Crab spiders come in bright yellow, pale pink, and stark white in order to sit on vibrant flora unseen. The spider might sit on top of the flower and remain motionless until opportunity strikes, or they may lurk on the underside of flowers for more cover.

They’re capable of taking down much larger animals, including wasps and bees. They do this by keeping them at an arm’s length. A very long arm’s length. Crab spiders have extra-long front arms that are used for grabbing onto prey and wrestling them into position for a kill-bite on the back of the neck. 

Even with these tools, this can be a challenging hunting method, like trying to catch a fly with chopsticks. Spiders can make several attempts where they get their little spider claws on prey only for it to getaway. However, on a sunny day on bright flowers, they have plenty of opportunities. The challenge then becomes surviving through a period of rainy days or bad weather. 

More Than Carnivores

A study in 1989 found that crab spiders can feed on nectar and pollen when insect prey is scarce. They found that spiderlings that fed on nectar and pollen had much better survival rates than ones that went through starvation periods. 

Ending: Take a look around you, put on your best colors, and make stopping to smell the flowers dangerous for bees and bugs.