Wikijunior:Bugs/Orb Weaver

What does it look like?
Orb Weaver Spiders vary greatly in size, shape, and color. Males are commonly smaller than females. They range from 1/16 to 1-1/8 inches long. They have 8 eyes. Four large eyes in front locate and catch prey. Small side eyes detect movement.

The exoskeleton (hard covering) is flexible so the spider can bend and move. The abdomen is very large. It can be brightly colored or patterned. Spiny Orb Weavers have spiny points on the abdomen. There are 4 pairs of legs. Three spiny claws on each leg are used to grip threads of the web. Other claws help the spider walk on hard surfaces. Some males have special spines on their legs to grasp prey.

Cross Spiders are named for the cross-like pattern of white dots on the abdomen. Araneus Orb Weavers are brown to orange. Their long legs are yellowish-brown, sometimes with black rings. Cucumber Spiders are pale green with spiny legs. Black-and-Yellow Orb Weavers have a black stripe with 4 white or yellow spots on the abdomen. Their legs are black with yellow-orange stripes.

Where does it live?
Orb Weaver Spiders are found worldwide. They live in the Americas, Africa, Australia, and Europe. There are none in Antarctica. They live in meadows, woods, grasslands, and gardens. Some are found in caves and other dark places. Several hundred species live in the deciduous forests of North America.

What does it eat?
Orb Weaver Spiders eat insects. They are known to eat small frogs and hummingbirds. Some species do not spin webs. Instead, they make a strand of silk with a sticky drop at the end. Some tropical species make huge strong webs that are able to catch birds.

How does it defend itself?
Orb Weaver Spiders are not aggressive. They run or drop off the web if threatened. They use camouflage to hide in leaf litter. Long-Jawed Orb Weavers have long jaws and legs, and thin bodies. They camouflage themselves by resting lengthwise along a twig or blade of grass. Variable Decoy Spiders place old egg sacs and other debris in their webs as camouflage.

What stages of metamorphosis does it go through?
Adult males do not spin webs. They wander around searching for a mate. Females sit on the web waiting for a male to come courting. Males pluck the web to let a female know they are looking for a mate. Otherwise, they might be mistaken for prey.

After mating, females weave silk egg sacs. They make many egg sacs, so if one is destroyed, the rest will be safe. A single egg sac has several hundred eggs. The egg sacs are hidden inside the web or buried in leaf litter. Females guard their eggs for a few days.

Orb Weaver Spiders go through simple, incomplete metamorphosis. There are only three stages: egg, spiderling, and adult. The eggs overwinter inside the egg sac. With warmer weather, spiderlings (newborn spiders) become active. They chew a hole in the egg sac wall and crawl out. When they emerge, they are blind and unable to eat. They look like small versions of adults. They grow by molting or shedding the outer covering of the body. Spiderlings can re-grow lost parts, such as legs, as long as they are growing and molting. After hatching, they remain nearby for a few days. Then they use a silk strand to float away on the wind.

What special behavior does it exhibit??
Orb Weaver Spiders hang upside down in the middle of the web. Doing this lets them wait for prey and check the web for damage. They make round webs with support lines. The support lines go out from the center to the edge of the web. They are not sticky and the spider can walk on them. The prey gets caught on the sticky spiral strands. Webs can be vertical, horizontal, or slanting. Orb Weavers catch their prey at night. Often, they replace the entire web in the evening. It takes about an hour to spin a new web. Males don't spin webs but will sometimes attach some webbing to the edge of the female’s web.

Yellow-and-Black Garden Spiders are called “writing spiders”. They make a zigzag pattern with the non-sticky support lines to stabilize the web. The pattern may help birds avoid flying into the web. It may help hide the spiders.

Female Crowned Orb Weavers make large webs that can be 16 inches across. They repair their webs by removing and eating tattered pieces. Then they spin new strands to rebuild it.

The Nephila species spins huge webs. In Papua, New Guinea their webs are used as fishing nets.

Orb Weaver Spiders produce seven different kinds of silk. Their spinnerets (silk spinning organs) can release one kind of silk or several kinds at once. They can combine several kinds to make a strong web. They use their back legs and spinnerets to measure distances on the web.

How does this bug affect people?
Orb Weaver Spiders are very docile and not dangerous to humans. They bite in self-defense. Their bite is often compared to a bee sting. The venom may cause an allergic reaction in some people.

They are beneficial because they catch and eat insect pests. They are nighttime hunters and help reduce mosquito populations.