Do Crab Spiders Make Webs? A Look at the Hunting Strategies of These Ambush Predators

A few of us took a short trip out to our family prairie last weekend. My daughter came home from college for the weekend and wanted to see what was going on in the prairie. So, we went canoeing (in small circles in a pond), hiking, and exploring. Later, I took pictures of dotted gayfeather seeds. While I was looking for more of those plants, I came across a grass leaf that was twisted in a funny way and held in place by some kind of white silk. Before my brain finally registered that I should go back and look at the grass leaf, I had already walked past it.

Looking more closely, I could see enough of the creature inside to identify it as a crab spider. Since it had been raining a lot for a few weeks, my first thought was that the crab spider had built a small shelter out of leaves. (Crab spiders don’t make webs, but like all spiders, do make silk and use it for various purposes. ). It looked more like a nest, though, and I thought it might have spider eggs inside. I took a lot of pictures of it for a few minutes because the wind was making it hard to keep the spider in one place.

Later, when I got home and looked through my photos, I was getting rid of the blurry ones of the spider because of the wind when I saw something that proved my guess. A tiny spiderling showed up right above an out-of-focus crab spider face, but only in one picture and not in any others. Apparently, this was indeed a crab spider nest, and at least one egg had already hatched.

Crab spiders aren’t the only group of spiders that take care of their kids. If you read this blog often, you may remember a post where I showed a mother wolf spider carrying her babies around on her body. If you don’t, you may have heard that wolf spiders carry both their egg sacs and their newly hatched babies around with them. But wolf spiders aren’t the only ones that care for their young. We are still learning more about how well different spider species do this. If you’re interested, you can read more in this nice blog post from Biome Ecology. If not, you can just join me in wishing this crab spider’s young luck as they go out and find safe places to spend the winter.

In several of our prairies right now, poppy mallows are among the most prolific flowers. You can wiggle your tongue around purple poppy mallow (Callirhoe involucrata) and pale pink poppy mallow (Callirhoe alcoides). They are also pretty flowers that pollinators need to eat. This week, I saw a monarch butterfly move from flower to flower in a big patch of pale pink poppy mallow, but I forgot to take a picture of it. When I stopped to take a picture of a poppy mallow flower yesterday, I noticed something odd about the bottom of the flower…

Those of you who have followed the blog for a while know of my affinity for crab spiders. They’re just so stinking cute, and once you start looking for them, they are everywhere, especially on flowers.

This friend with long legs and his family were this week on a variety of flowers in our prairies, such as the pale pink poppy mallow (above) and the yarrow (below).

This is a different crab spider that I saw at our family prairie. It was sitting on yarrow with its long front legs cocked and ready to snap shut on any unwary prey.

An insect landed on the flower and began eating pollen while I took pictures of the spider. The fly then moved around the flower.

It got closer and closer to the spider, so I just kept shooting. A few moments later, it turned its back on the spider….

…and the spider GRABBED it. The fly made a lot of noise and pushed the spider around a bit, but the strong grip and poisonous bite of the spider beat it.

For a few seconds, the spider stood vertically, holding tight to the fly. Then as the fly’s struggles subsided, the crab spider repositioned itself to start feeding.

It turns out that the best place to prick a fly to get its liquid insides out is right behind the head. A little tip for all you fly sucker wannabes out there….

The large number of flowers and the ease with which this crab spider caught its prey make me think of how dangerous it is to be a pollinator. Every flower could be a healthy food source, but many of them are also home to crab spiders that are waiting to pounce on careless bugs. Since I try to take pictures of pollinators all the time, I’m very aware of how quickly they move from flower to flower. Yes, they do. The longer they stay near a flower, the more likely it is that something will catch them and eat them.

Crab spiders are a fascinating group of spiders with a distinctive hunting strategy They don’t spin elaborate webs like orb weavers – instead they are ambush predators that lurk and wait for prey But do crab spiders make any webs at all? Let’s take a closer look at how these crafty arachnids hunt and use silk.

Over 1,200 species of crab spiders exist belonging to the Thomisidae family. Here are some key facts about their biology and behavior

Called crab spiders for their crab-like appearance – they hold their front two legs outstretched like pincers.
Found worldwide in a diverse range of habitats from grasslands to forests.
Adults reach 0.2 – 0.8 inches long usually, with females larger than males.
Variable coloring, from white to yellow to green, helps them camouflage.
Are ambush predators rather than web builders. Sit and wait stealthily for prey.
Can walk sideways and backwards rapidly like crabs.
Prey on flies, bees, butterflies and more by grabbing them quickly.
Some species can change color to better match their surroundings over days or weeks.

Crab Spiders Don’t Make Traditional Prey-Catching Webs

The key thing to know is that crab spiders do not construct complex webs for catching prey, unlike orb weaver spiders and cobweb spiders. Some reasons why:

Their hunting strategy depends on stealth and surprise attacks rather than traps.
They need mobility to ambush prey in different locations. Large webs would hinder this.
The time and energy spent on spinning big webs is better used for ambushing.
They can grip and subdue prey quickly with their front legs once in striking range.

So while crab spiders do produce silk, they do not use it to build sticky spiraled webs to passively catch prey like many spiders. Their hunting approach requires different adaptations.

How Crab Spiders Use Silk

Though they don’t create sprawling trap webs, crab spiders do use silk in more limited ways:

Anchoring themselves – They will anchor themselves with silk to a plant or flower while hunting to avoid being spotted by prey.
Rafting – Juvenile crab spiders disperse by ballooning on silk strands and silk is used if they land in water.
Egg sacs – Females encase their eggs in a silk egg sac attached to vegetation.
Nests and shelters – Some speculated uses of silk include building nests or shelters, though more research is needed.

So while minimal, crab spiders employ silk for mobility, reproduction, and shelter like other spiders. But silk isn’t a key part of their actual hunting strategy.

Crab Spider Hunting Techniques

Rather than big webs, crab spiders have evolved superb ambush hunting methods:

Stealth and camouflage – They stay incredibly still and blend in with surroundings. This allows close proximity to prey.
Speed and agility – They can lunge rapidly and strike prey decisively. Their sideways mobility aids this.
Strength and venom – Once they grab prey, their strong front legs and venom quickly overpower and kill it.
Flexibility – Some can change color to match different flowers they hunt on.
Patience – Waiting motionless for long periods for prey to come near.

These tactics maximize their chances for surprise attacks. Web building would sacrifice secrecy and speed for these lurking hunters.

Prime Ambush Sites

Crab spiders don’t build webs, but they do seek out prime sites for launching ambushes:

On flowers – They blend in with petals and grab pollinators.
Among leaves – They hide on foliage and snatch any insects that land.
On branches – Positioned to pick off prey and rappel away via silk strands if disturbed.
In grass – Concealed in vegetation to surprise passing ground prey.

By keeping still in these spots and utilizing camouflage, crab spiders put themselves in a position for high success.

Crab Spider Webs – A Recap

While other spiders use webs as snares, crab spiders utilize an ambush approach. Here’s a summary:

They do not construct prey-catching webs due to their hunting strategy.
Limited silk use includes anchoring, dispersal, nests, and egg sacs.
Stealth, speed, venom and camouflage allow them to hunt successfully.
They pick strategic ambush sites to maximize their proximity to prey.

So crab spiders may not produce intricate webs, but they have mastered the art of stealthy ambush hunting thanks to their unique adaptations and skills. While often overlooked, their unusual techniques highlight the diverse hunting methods of spiders.

do crab spiders make webs

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A crab spider and silk webbing at our family last weekend.

A tiny spiderling, accidentally photographed.

The crab spider eventually shifted around and showed its face.

This friend with long legs and his family were this week on a variety of flowers in our prairies, such as the pale pink poppy mallow (above) and the yarrow (below).

This is a different crab spider that I saw at our family prairie. It was sitting on yarrow with its long front legs cocked and ready to snap shut on any unwary prey.

An insect landed on the flower and began eating pollen while I took pictures of the spider. The fly then moved around the flower.

It got closer and closer to the spider, so I just kept shooting. A few moments later, it turned its back on the spider….

…and the spider GRABBED it. The fly made a lot of noise and pushed the spider around a bit, but the strong grip and poisonous bite of the spider beat it.

For a few seconds, the spider stood vertically, holding tight to the fly. Then as the fly’s struggles subsided, the crab spider repositioned itself to start feeding.

It turns out that the best place to prick a fly to get its liquid insides out is right behind the head. A little tip for all you fly sucker wannabes out there….

How do spiders spin webs across LONG DISTANCES?

Do green crab spiders make webs?

Green crab spiders do not make webs to catch prey. Both sexes spin silk for different purposes. The males cover their mate with silk whose size could be double theirs. Whereas, the female green crab spiders use it to make the sac for laying eggs. Are Green Crab Spiders Venomous? Yes, Green Crab Spiders are venomous.

Do crab spiders weave webs?

3 Incredible Crab Spider Facts! Crab spiders don’t weave webs and are mostly ambush predators. They can change color to blend into their surroundings, though this can take a long time. Female crab spiders tend to be larger than males, and in species such as Misumena vatia, females are many times bigger than males.

Do all spiders make webs?

Although webs are the most well-known use for spider silk, not all spiders make webs to catch their prey. In fact, less than half of the 37 spider families in Britain do.

How do crab spiders develop?

Crab spiders develop via gradual metamorphosis, meaning they hatch from an egg and undergo several molts as a juvenile before eventually becoming a reproductive adult without entering a pupal stage. Most crab spiders species will have one generation per year in Ohio. They overwinter as either eggs or immatures. (Photo Kim Moore).