Wikijunior:Bugs/Crab Spider

What does it look like?
Crab Spiders are named for their shape and the way they move. They shuffle sideways and backward like crabs. They hold their front legs out like crab claws. They have 4 pairs of legs. The first 2 pairs of legs are large with spines. The hard outer covering (carapace) is round, short, or sometimes long. The abdomen is broad at the end. The abdomen often has a pattern. Crab Spiders come in many different colors.

They have a distinctive eye pattern. There are 2 curved rows of eyes. Each row has 4 eyes. The Six-eyed Crab Spider has 6 small eyes.

Males and females do not look alike. The female’s pedipalps (feelers) look like little legs. The ends of the male’s pedipalps look like boxing gloves. South American Seven-Spined Crab Spiders are very small (less than ½ of an inch). European Hairy Crab Spiders are even smaller (about ¼ of an inch). Giant Crab Spiders are very large. They can be 3 inches with their legs spread out.

Where does it live?
Crab Spiders live all over the world. Most live in warm and humid, tropical places. Giant Crab Spiders are called banana spiders because they live in bunches of bananas.

Crab Spiders are found in meadows and gardens. They live on flowers, plants, and tree bark. Slender Crab Spiders live in damp meadows.

Goldenrod Crab Spiders are common throughout Europe and North America. They can change from one color to another to match the flowers.

What does it eat?
Crab Spiders eat insects, including bumblebees and butterflies. Crab Spiders rest on a flower waiting for prey. Tiny hairs on their body and legs sense vibrations made by insects. When an insect comes to the flower for nectar, the spider uses its long front legs to catch and hold it.

How does it defend itself?
The main enemies of Crab Spiders are birds and wasps. Crab Spiders use their long legs to run away from predators. They have camouflage for protection. They hide in plain sight by matching the color of the flower they are on. The Australian White Crab Spider hides in white flowers. A Goldenrod Crab Spider can be found sitting inside goldenrod blooms.

A Slender Crab Spider hides itself by lying lengthwise on a blade of grass. It hugs the grass with its legs. Its head points downward.

What stages of metamorphosis does it go through?
Crab Spiders undergo simple, incomplete metamorphosis. There is no larval or pupal stage. There is no “resting” stage. Females spin a thick silken sheet for their eggs. The eggs rest in a flat sac attached to a plant. The egg sac holds them together and protects them from bad weather.

The eggs hatch in about 3 weeks. Spiderlings (newborn spiders) chew a hole in the wall of the egg sac so they can escape. When spiderlings emerge from the eggs, they look like small versions of adults.

A spiderling has a hard outer covering (exoskeleton). As its body grows, the exoskeleton becomes too tight. The spiderling needs more room to grow. Its heart pumps blood to puff out its body and break open the exoskeleton. The spiderling comes out covered in a new, soft exoskeleton. It needs to do this 4 to 7 times to become an adult.

What special behavior does it exhibit?
A Crab Spider’s silk is liquid at first. The spider attaches it to something and pulls. The liquid turns to a solid silk strand.

Crab Spiders are known as free-living spiders or wandering spiders. They are hunters and do not need webs to catch food. They can sit on a flower for many days without moving.

The Costa Rican Leaf-mimic Crab Spider looks like a dead leaf attached to a stem. The Madagascar Warty Bird-dropping Crab Spider looks like bird waste.

The female North American Goldenrod Crab Spider can change from yellow to white and back again. She can catch prey on both flower colors. The yellow color takes about a week to make. Becoming white again takes less time, because the yellow color passes out of its body.

The Weaver Ant Mimic Crab Spider mimics weaver ants. It holds its front legs like antennae so it looks like it has only 6 legs.

If a male Crab Spider gets bitten on a leg, it snaps off the leg to keep the venom from getting into its body.

How does this bug affect people?
Crab Spiders help keep insect populations from getting too big. They eat harmful insects, but they also eat good insects like honeybees. Without honeybees, plants and flowers cannot be pollinated and honey cannot be made.

If disturbed, Crab Spiders may bite people. Their venom is not harmful. Their bite leaves a puncture wound and may cause an allergic reaction.