Marbled orb weavers are colorful spiders known for their distinctive, large abdomens.
These spiders display a wide range of colors, including white, yellow, orange, tan, grayish, and even purple.
Their patterns vary, but they commonly have mottling and spotting of black, brown, or purple on their abdomens.
As interesting as they are to look at, many people wonder if marbled orb weavers are poisonous.
While their bites can be slightly painful, they are not considered dangerous to humans.
Their venom is not potent enough to cause severe reactions, making encounters with these spiders fairly low risk.
Are Marbled Orb Weavers Poisonous?
While marbled orb weavers are venomous in the sense that they use venom to subdue their prey, they are not considered dangerous to humans2.
Their venom is not potent enough to cause significant harm or severe reactions in people.
In fact, bites from these spiders are quite rare and mostly occur when the spider feels threatened or accidentally comes into contact with a human.
In comparison to other venomous spiders such as the black widow or brown recluse, the marbled orb weaver has a relatively low risk of causing serious harm3.
The bite of a marbled orb weaver may cause some localized pain, itching, and mild swelling, but these symptoms usually subside within a short period of time.
There is also a low likelihood of an allergic reaction to the venom.
To help illustrate the differences in venom, here is a comparison table:
| Spider | Danger to Humans | Venom Potency |
|---|---|---|
| Marbled Orb Weaver | Low | Mild |
| Black Widow | High | Potent |
| Brown Recluse | High | Potent |
Classification and Taxonomy
The Marbled Orb Weaver belongs to the family Araneidae and the genus Araneus within the class Arachnida. This makes them part of the larger orb weaver spider group.
Here is a brief overview of the spider’s classification:
- Class: Arachnida
- Family: Araneidae
- Genus: Araneus
- Scientific name: Araneus marmoreus Clerck
Comparing Marbled Orb Weavers with other orb weavers, a key standout is their distinct appearance.
For instance:
| Feature | Marbled Orb Weaver | Other Orb Weavers |
|---|---|---|
| Abdomen shape | Large and marbled | Smaller, diverse shapes |
| Colorations | Orange, yellow, white, grayish | Typically brown or beige |
| Pattern | Marbled, variable patterns | Simple, less detailed patterns |
Physical Description and Identification
The marbled orb weaver spider has a distinct appearance.
Females usually measure 9 to 20 millimeters in length with a large abdomen that varies in color, commonly found to be orange with brown or purple markings and yellow spots.
On occasion, abdomens may be nearly white. The cephalothorax (head) is typically yellow or burnt-orange, displaying a central dark line and additional lines on either side 1.
This species can be recognized by its:
- Large, colorful abdomens
- Dark markings on yellow or burnt-orange cephalothoraxes
- Presence of a central dark line and additional lines on either side of the cephalothorax
Habitat and Distribution
North America
Marbled orb weavers are widely distributed across North America, including regions like Canada, Texas, and North Dakota.
They inhabit wooded areas, particularly near edges of forests or alongside streams. Some common locations to find these spiders include:
- Alaska
- Oregon
- South Carolina
- North America’s Atlantic coast
Europe
Marbled orbweavers can also be found in Europe, although their distribution varies across the continent. In general, these spiders prefer wooded habitats in both warmer and cooler climates.
Asia
In Asia, marbled orbweavers have been spotted in countries like Japan.
Similar to their North American and European counterparts, they reside in varied forest environments and often establish their webs close to water sources.
Table showing the distribution of marbled orb weavers
| Continent | Distribution | Habitat |
|---|---|---|
| North America | Canada, Texas, North Dakota, etc. | Wooded areas, forest edges, streams |
| Europe | Varies across the continent | Wooded habitats, warm and cool climates |
| Asia | Japan, and likely other countries | Forests, near water sources |
Web and Hunting Behavior
Marbled orb weavers create intricate webs made of silk. Their webs are a type of orb web, which has a circular pattern.
The main features of these webs are:
- Circular pattern: Orb-shaped designs composed of radial and sticky spiral lines
- Signal thread: A non-sticky thread that helps detect prey by vibrating when disturbed
Moreover, orb webs offer a couple of advantages, such as:
- Efficient in capturing flying insects
- Provide a large surface area for prey to get trapped
However, there can be some drawbacks:
- Requires continuous rebuilding as they can get easily damaged
- Can be time-consuming to construct for the spider
Capturing Preys
Marbled orb weavers are skilled hunters, primarily feeding on flying insects. Their capture strategy involves two key elements:
- Web construction: They build their orb webs at locations with high insect traffic, increasing the probability of capturing prey
- Prey sensing: When an insect gets trapped in the web, the spider detects the movement through the signal thread and rushes to subdue its prey
Therefore, marbled orb weavers are proficient predators, relying on their orb-shaped webs and keen senses to trap and capture their meals.
Reproduction and Lifespan
Courtship
Male and female marbled orb weavers engage in a fascinating courtship process. The male typically vibrates his legs to attract the female’s attention, and if she is receptive, they mate.
Laying Eggs
Once mating is successful, the female lays her eggs – which can number in the hundreds.
She then creates an egg sac to protect them during development, often placing it in a hidden or guarded area.
Spiderling Development
The development of spiderlings within the egg sac is as follows:
- Eggs hatch within the sac
- Spiderlings grow and molt several times
- Once fully developed, they emerge from the sac
Therefore, male and female spiders each have distinct roles, and their lifespans differ as well.
Ecological Significance and Relationships
Marbled orb weaver spiders play a crucial role in their ecosystem as prolific predators. They prey on a variety of insects, such as:
- Flies
- Mosquitoes
- Moths
Their presence helps control insect populations in their habitats.
Conversely, orb weaver spiders can fall prey to predators like birds and certain wasps. For example, the parasitic wasp larvae can consume the spider’s abdomen as a source of nutrition.
Parasites and Commensals
Marbled orb weavers also share their ecosystem with organisms that have different relationships with them.
One example is the spiders from the family Theridiidae, which are known as tangle-web or cobweb spiders.
These spiders may live in close proximity to marbled orb weavers without any direct harm.
In contrast, certain parasites can have negative effects on orb weaver spiders.
Some cases even involve parasitic wasp species as mentioned before, laying eggs on the spiders themselves.
Marbled orb weavers and the closely related Argiope garden spiders can both be found in similar habitats.
They both contribute to the ecosystem by limiting insect populations as predators.
Comparison of Marbled Orb Weavers and Argiope Garden Spiders
| Feature | Marbled Orb Weaver | Argiope Garden Spider |
|---|---|---|
| Size | 9 to 20 millimeters (adult females) | 14 to 25 millimeters (adult females) |
| Web | Orb-shaped webs | Orb-shaped webs with a zigzag pattern known as “stabilimentum” |
| Habitat | Forest edges, meadows, and gardens | Forest edges, meadows, and gardens |
| Coloration | Orange, brown, yellow, or white with varying markings | Black and yellow markings on the abdomen |
Therefore, marbled orb weavers participate in complex ecological relationships as predators, prey, hosts, and neighbors to various species.
While they are not poisonous to humans, their presence contributes to the balance of their ecosystem.
Conclusion
The marbled orb weaver, with its captivating appearance and unique web-building skills, stands out as an intriguing inhabitant of wooded landscapes across North America, Europe, and Asia.
While marbled orb weavers are venomous, their venom poses minimal risk to humans, causing only mild, temporary symptoms.
These spiders play a vital role as skilled predators, helping control insect populations and participating in intricate ecological interactions.
Their presence enriches the delicate balance of their habitats, reflecting the interconnected nature of all species in the natural world.
Footnotes
2 Comments. Leave new
Are these spiders poisonous? We live in Delta junction Alaska and have only seen them this summer.
Orbweavers pose no threat to humans.