What Do Orb Weaver Spiders Eat?

Orb Weaver Spiders, Family Araneidae

Habits and Traits of These Arachnids

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  • B.A., Political Science, Rutgers University

When you think of a spider, you probably picture a big, round web with its resident spider poised in the center, waiting for a hapless fly to land in the web’s sticky strands. With few exceptions, you would be thinking of an orb weaver spider of the family Araneidae. The orb weavers are one of the three largest spider groups.

The Family Araneidae

The family Araneidae is diverse; orb weavers vary in colors, sizes, and shapes. The webs of orb weavers consist of radial strands, like spokes of a wheel, and concentric circles. Most orb weavers build their webs vertically, attaching them to branches, stems, or manmade structures. Araneidae webs may be quite large, spanning several feet in width.

All members of the family Araneidae possess eight similar eyes, arranged in two rows of four eyes each. Despite this, they have rather poor eyesight and rely on vibrations within the web to alert them to meals. Orb weavers have four to six spinnerets, from which they produce strands of silk. Many orb weavers are brightly colored and have hairy or spiny legs.

Classification of Orb Weavers

Kingdom — Animalia
Phylum — Arthropoda
Class – Arachnida
Order – Araneae
Family — Araneidae

The Orb Weaver Diet

Like all spiders, orb weavers are carnivores. They feed primarily on insects and other small organisms entrapped in their sticky webs. Some larger orb weavers may even consume hummingbirds or frogs they’ve successfully ensnared.

The Orb Weaver Life Cycle

Male orb weavers occupy most of their time with finding a mate. Most males are much smaller than females, and after mating may become her next meal. The female waits on or near her web, letting the males come to her. She lays eggs in clutches of several hundred, encased in a sac. In areas with cold winters, the female orb weaver will lay a large clutch in the fall and wrap it in thick silk. She will die when the first frost arrives, leaving her babies to hatch in the spring. Orb weavers live one to two years, on average.

Special Orb Weaver Adaptations and Defenses

The orb weaver’s web is a masterful creation, designed to ensnare meals efficiently. The spokes of the web are primarily non-sticky silk and serve as walkways for the spider to move about the web. The circular strands do the dirty work. Insects become stuck to these sticky threads on contact.

Most orb weavers are nocturnal. During daylight hours, the spider may retreat to a nearby branch or leaf but will spin a trapline from the web. Any slight vibration of the web will travel down the trapline, alerting her to a potential catch. The orb weaver possesses venom, which she uses to immobilize her prey.

When threatened by people or most anything larger than herself, an orb weaver’s first response is to flee. Rarely, if handled, will she bite; when she does, the bite is mild.

Orb Weaver Range and Distribution

Orb weaver spiders live throughout the world, with the exceptions of the Arctic and Antarctic regions. In North America, there are approximately 180 species of orb weavers. Worldwide, arachnologists describe over 3,500 species in the family Araneidae.

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Orb-Weaver Spiders

SCIENTIFIC NAME

APPEARANCE

The orb weaver spider group is comprised of a large number of species thus making it difficult to distinguish them from other spider groups and from each other. In fact, the Orb-weaver spider family, Araneidae, is one of the most variable in size and appearance of all spider families. However, the most observable appearance of orb weavers isn’t necessarily their appearance, but the appearance of the large webs they create. In general, orb weavers construct organized, circular grid webs that are similar in shape to webs depicted in Halloween decorations. More specifically, orb weaver webs are made of radial strands of silk that look like the spokes of a wheel with the spokes connected by numerous concentric circular silk strands. The web of the garden orb weaver spider is very large and can measure up to three feet in diameter. When observed in their natural habitats, orb weavers will usually be seen hanging head down in their web.

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Like all other spiders, orb weavers have a cephalothorax (a fused-together head and thorax), abdomen, 8 legs and fang-like mouthparts called chelicera. Many orb weavers are brightly colored, have hairy or spiny legs and a relatively large abdomen that overlaps the back edge of the cephalothorax. Abdomens vary between species. Some orb-weaver spiders have spiny, smooth, or irregularly shaped abdomens. Most nocturnal orb weavers are usually brown or gray in color. Diurnal species exhibit bright colors of yellow or orange along with black markings.

BEHAVIOR, DIET AND HABITS

Orb weavers are typically nocturnal spiders and many species will build or do repair work on their webs at night. Some orb weaver spiders tear down and even consume much of the web’s silk as the morning begins to dawn. This interesting habit is performed in order take in moisture from dew that may have settled on the web and to prevent large animals such as birds from getting caught in the web.

Since orb weavers are not hunters or wanderers, they will sit in their web or perhaps move off their web and wait for prey to get tangled in their web. Should the spider move off the web, it will remain nearby and hidden in a protected site such as some rolled up leaves or on the branch of a plant. However, the spider remains aware of prey that may become trapped in the web by a trap line of silk that will vibrate and alert the spider if something enters the web. If a prey insect is trapped in the web, the trap line vibrates notifying the spider rush to the web, bite and paralyze the prey and wrap it in silk for later consumption. If something non-eatable is trapped, the spider will either just ignore it or remove it from the web and go back to its protected hiding place. Orb weavers are most often noticed by homeowners in the late summer and fall since the adult spiders have attained their largest size and have constructed the largest number of webs.

Small insects such as flies, moths, beetles, wasps and mosquitoes are examples of insects that make up the spider’s diet. Some of the larger orb weavers may also trap and eat small frogs and humming birds should they venture into the web. Orb weavers tend to inhabit locations where there is abundant prey and structures that can support their web. Typical habitats include areas around night-lights, tree branches, tall grass, weeds, fences, walls and bushes.

REPRODUCTION

Male orb weavers are much smaller than females and the male’s role in to mate with the female. Since the males are small, it is not uncommon for them to become the female’s first meal after mating. Female orb weavers produce one or more egg sacs and each sac may contain up to several hundred eggs.

SIGNS OF AN INFESTATION

Presence of the web is the most obvious sign of an orb weaver population

DISTRIBUTION

Orb weavers are found throughout the world, except for the Arctic and Antarctica. In North America, there are approximately 180 species of orb weaver spiders.

MORE INFORMATION

Despite their large size and fearsome appearance, orb weavers are not considered to be medically important. Orb weavers rarely bite and only do so when threatened and unable to escape. If bitten by an orb weaver, the bite and injected venom is comparable to that of a bee sting, with no long-term implications unless the bite victim happens to be hyper-allergic to the venom.

Preventing orb weaver spiders is usually unnecessary unless an orb weaver builds a web in a location frequented by people, in which case someone could be adversely affected by arachnophobia, the extreme fear of spiders. Some key preventive things a homeowner can do is reduce the population of insects that serve as food for spiders, seal up holes, cracks and gaps in the home’s exterior to prevent entrance by spiders into the home’s living spaces and remove ground litter and other sites that serve as spider harborage. Should the homeowner need assistance in control of these or any other spiders, contact your pest management professional (PMP) and request an inspection. Your PMP can then use his inspection findings to prepare a comprehensive pest management plan that will effectively and efficiently deal with the specific pest problem.

Spiders in the family, Uloboridae, commonly known as the hackle-band orb weavers are unique since they do not possess venom, the only family of spiders in the United States with this characteristic.

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Orb Weaver Spider

Prolific throughout entire continental United States, Canada, Alaska, and Hawaii.

Anywhere with abundant prey and structures to support the web – around light fixtures used at night, or tree branches, tall grasses, and bushes.

Most noticeable in late summer in fall, when webs and adults reach their largest size.

Food sources vary, but typically any small insects they catch in their webs. Some of the bigger orb weavers (Argiope genus) have been observed eating small frogs and humming birds (only if ensnared within the web).

Most orb weavers appear in the spring, but are not noticed until summer to fall.

The adult males will wander in search of a mate, and as such, typically do not stay on a web for long, if they spin a web at all. Adult males are not observed as much as the females, since they are always on the move, looking for that “Mrs. Right”. Typically after mating, the males will die.

The most commonly noticed orb weaver is female, since she sits on her web, feeding and eventually waiting for the males to find her. Toward the end of fall, the females will lay their last clutch of eggs, and then die at the first frost. The eggs can survive the winter (even withstanding freezing) due to the simplistic nature/chemistry of the eggs. The warmth of the spring will cause the eggs to mature, releasing a new generation of orb weavers.

A single egg sac can contain upwards of several hundred eggs. Juvenile orb weavers will spin “perfect” orb webs, but as they mature, the webs will become more distinctive and adapted for that particular species. (1)

Orb weavers are very docile, non-aggressive spiders that will flee at the first sign of a threat (typically they will run or drop off the web). They are not dangerous to people & pets, and are actually quite beneficial because they will catch and eat a lot of pest-type insects.

Put a medium-sized insect in the web of a large orbweaving spider in the garden. You will see the spider bite the prey, wrap it in silk, wait for it to die, then begin to eat. As a first step in eating, the spider will literally vomit digestive fluid over the prey. Then the prey is chewed with the “jaws” (chelicerae), and the fluid is sucked back into the mouth together with some liquefied “meat” from the prey. The spider repeats this process as often as necessary to digest, and ingest, all but the inedible hard parts. What is discarded afterwards is a small ball of residue. (2)

Being bitten by an orb weaver is very uncommon, and typically the individual was “asking” to be bitten. Orb weavers will only bite if they feel threatened and trapped without a chance for escape (e.g. – like trying to pick them up). A bite is often compared to a bee sting, and for most people, is nothing serious. However, it is recommended to observe them in their environments (e.g. – on their web) and not to pick them up.

Orb weavers are typically nocturnal. During the day, the spider will prefer to either sit motionless in the web or move off the web. If the spider moves off the web (but does not abandon it), she will be nearby in some cover (rolled up leaves, or on a branch) with a trap line nearby. If prey becomes ensnared in the web, the trap line will vibrate, indicating a possible meal. The spider will investigate; if it is “meal worthy”, she will bite it to immobilize it, and wrap it with silk to either eat later, or to continue to subdue the meal while eating. If the trapped insect is not meal worthy, she will ignore it or eject it from the web.

At night, the orb weaver will become more active, working to repair any damage on the web, and sitting in the middle of the web. For some species, once morning starts to arrive, the spider will tear down the web and eat most of the silk (reabsorption of moisture plus consuming any dew that might have settled on the web). They will rebuild their web at dusk/night.

www.wildlifeheritage.org

Critter Catalog

  • Information
  • Pictures
  • Classification

Local animals in this group:

Additional information:

Find information at

Araneidae

What do they look like?

All spiders have two body-segments, a cephalothorax in front and an abdomen behind. They have eight legs, all attached to the cephalothorax. On the front they have two small «mini-legs» called palps. These are used to grab prey. They are also used in mating. Palps are much bigger in male spiders than in females. All orbweavers have fangs that they use to bite their prey with. They all have venom glands that produce toxins. The toxins paralyze and digest their prey.

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Orb-weavers are more diverse physically than the other groups of spiders. They usually have a fairly large abdomen, and it nearly always overlaps the back of the back edge of the cephalothorax. The shape of the abdomen varies a lot between species. Sometimes it is spiny, sometimes smooth, sometimes very irregular in shape. Nocturnal orb-weavers are usually brown or gray. Diurnal species are more brightly colored and may be black and yellow or orange. Often females are much larger than males in this group.

  • Other Physical Features
  • ectothermic
  • bilateral symmetry
  • Sexual Dimorphism
  • female larger
  • sexes shaped differently
  • Range length 3.0 to 30.0 mm 0.12 to 1.18 in

Where do they live?

Orb-weaving spiders are found all around the world. There are over 4000 species known, and probably at least that many still unknown to science. In Michigan there are at least 40 species known, and probably more still out there.

What kind of habitat do they need?

Orb-weavers live anywhere there are insects and places to put up their webs. They are much more common in humid habitats than in dry ones.

  • These animals are found in the following types of habitat
  • temperate
  • tropical
  • terrestrial
  • Terrestrial Biomes
  • tundra
  • taiga
  • desert or dune
  • chaparral
  • forest
  • rainforest
  • scrub forest
  • mountains
  • Wetlands
  • marsh
  • swamp
  • bog

How do they grow?

Spiders hatch from eggs. The hatchlings look more or less like grown-up spiders, though sometimes their colors change as they age. To grow they have to shed their exoskeleton. They do this many times during their lives.

How long do they live?

Adult Orb-weavers can’t usually survive below-freezing weather, so they don’t live for more than a year. In tropical regions with warm winters, they may live longer.

How do they behave?

Sometimes males build small webs around the web of a female, perhaps living there while waiting for her to finish growing. Otherwise spiders in this family are not social, they each build their own web and stay with it. As noted above, some species hunt at night, others are active during the day.

  • Key Behaviors
  • diurnal
  • nocturnal
  • motile
  • sedentary
  • solitary

How do they communicate with each other?

Communication among orb-weavers is mostly by touch and web vibrations, though there are probably some chemical signals too. Their vision is not good enough for much visual communication.

What do they eat?

These spiders catch and eat the insects they trap in their webs. When an insect touches the sticky web it gets caught. They spider quickly rushes in and starts spinning and wrapping the insect in more webbing to keep it trapped. The orb web is very distinctive, and is the easiest way to tell that a spider belongs to this group. Orb webs are flat, and have a neat spiral of sticky silk that goes around and around from the middle to the outer edge. Many species in this family build a new web every day or every night, and then take it down and eat it before hiding for the night or day.

  • Primary Diet
  • carnivore

What eats them and how do they avoid being eaten?

Many orb-weavers only put up their webs at night, in order to avoid birds. Orb-weavers with webs up in daylight are more brightly colored, maybe to warn predators of their venomous bite. If disturbed in their webs, many orb-weavers quickly drop away.

  • Known Predators
    • predatory wasps
    • parasitic wasps
    • other spiders
    • insect-eating birds
    • beetles (eat the eggs)

What roles do they have in the ecosystem?

Orb-weavers are predators that are usually low in the food web. They eat insects but are in turn eaten by other predators.

Do they cause problems?

Orb-weaver spiders can bite, and are venomous, but none of them are known to be particularly dangerous to people.

  • Ways that these animals might be a problem for humans
  • injures humans
    • bites or stings

How do they interact with us?

Orb-weavers, like most spiders, are important predators of pest insects.

  • Ways that people benefit from these animals:
  • controls pest population

Are they endangered?

No orb-weavers are known to be endangered, but since many species are still not known to scientists, there could be rare ones out there we don’t know about.

  • IUCN Red List [Link] Not Evaluated

Some more information.

Charlotte, the spider in the book «Charlotte’s Web,» belonged to this family of spiders.

Contributors

George Hammond (author), Animal Diversity Web.

Hammond, G. . «Araneidae» (On-line), Animal Diversity Web. Accessed June 11, 2020 at http://www.biokids.umich.edu/accounts/Araneidae/

BioKIDS is sponsored in part by the Interagency Education Research Initiative. It is a partnership of the University of Michigan School of Education, University of Michigan Museum of Zoology, and the Detroit Public Schools. This material is based upon work supported by the National Science Foundation under Grant DRL-0628151.
Copyright © 2002-2020, The Regents of the University of Michigan. All rights reserved.

www.biokids.umich.edu

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