The Darwin’s bark spider is a special member of the orb-weaver family. They make the biggest orb webs, some even as big as 28000 sq. cm! Named after the famous Charles Darwin, this spider has a lot of interesting facts.
Size: Adult Darwin’s bark spiders exhibit sexual dimorphism. Females range from 0.7 – 0.9 inches (1.7 – 2.2 cm) in size while males are significantly smaller, about 0.2 inches (0.5 cm).
Color: Females flaunt a striking black body adorned with white hairs on their cephalothorax, appendages, and abdomen. Males exhibit a light brown or reddish color, also highlighted with white hairs similarly arranged as the females..
Other Characteristic Features: Unique to the females are the two pairs of humps on their cephalothorax, while males are distinguished by their palpal bulbs, equipped with a straight-tipped conductor and a distinct spoon-shaped embolus.
Eggs
Female Darwin’s bark spiders weave a protective sac to deposit their eggs.
Spiderlings
While detailed observations of the spiderlings are minimal, it’s believed they follow the typical arachnid lifecycle, venturing off independently once they reach a certain level of maturity.
The Web
The Darwin’s bark spider’s web is a feat of biological material engineering, with some webs spanning three feet wide and boasting a tensile strength ten times greater than Kevlar. Strategically built over water bodies, the orb part of the web hovers above the surface, enabling the spider to ensnare aquatic insects like mayflies, which frequently populate such environments.
Are Darwin’s Bark Spiders Venomous?
Yes, Darwin’s Bark Spiders have venom which they use mainly to paralyze their prey.
Can Darwin’s Bark Spiders Bite?
Yes, they can bite if threatened, but their venom is generally not harmful to humans, and their bite causes minor discomfort.
Ecological Importance and Behavior of Darwin’s Bark Spider
The Darwin’s bark spider’s choice of habitat—near water bodies—allows it to exploit a niche where aerial and aquatic ecosystems intersect. Their web-building not only serves as a means to catch prey but also contributes to the balance of insect populations, especially mayflies. Furthermore, the silk produced by these spiders is the strongest known to science, indicative of their evolutionary success and remarkable survival strategies.
Natural Predators: The magnificent webs of these spiders, while strong, cannot fully protect them from natural predators. Birds, larger insects, and perhaps small mammals pose a threat to Darwin’s bark spiders, making their life cycle one of constant vigilance and adaptation.
Prey-Predator Dynamics: Darwin’s bark spiders play a dual role in their ecosystems. As predators, they are lethal to the mayflies and other insects they consume, impacting the population dynamics of their prey. As prey themselves, they must constantly innovate to avoid predation, leading to the evolution of their remarkable web strength and construction techniques.
Relationship with Humans: Humans rarely encounter Darwin’s bark spiders, as their habitats are typically remote and in close proximity to water bodies. While they are not a threat to humans, the silk produced by these spiders has garnered interest for its potential applications in materials science due to its incredible strength and elasticity.
Quick Facts
Distribution
Madagascar
Habitat
Near waterbodies
Web Type
Orb web
Diet
Mayflies and other aquatic insects
IUCN Conservation Status
Not Listed
Did You Know
Darwin’s bark spider’s web is the largest, strongest, and most complex worldwide. The web’s bridge line could extend up to 82 ft, and the spider can cross a river depending on its web. The silk that it produces is the strongest among all spider species.
Their discovery dates back to the year 2009, in Madagascar’s Andasibe-Mantadia National Park.
The female spider either eats the male counterpart or castrates it post-copulation.
In summary, the Darwin’s bark spider is a master of its craft, shaping its environment through its extraordinary web-building.
Darwin’s bark spiders show significant sexual dimorphism in their size. Adult females are quite large, ranging from 0.7 to 0.9 inches, while males are much smaller, typically measuring only about 0.2 inches. This considerable size difference is a key characteristic of the species.
The silk produced by a Darwin’s bark spider is exceptionally strong and tough. Scientific analysis shows its tensile strength is approximately ten times greater than that of Kevlar, a synthetic fiber used in body armor. This makes it one of the most durable biological materials known to science.
Darwin’s bark spiders build their large webs over water bodies to effectively hunt their preferred prey. This strategic placement allows them to capture aquatic insects, such as mayflies, that frequently emerge from the water’s surface. The web’s orb section hovers just above the water for this purpose.
No, Darwin’s bark spiders are not considered dangerous to humans. Although they possess venom to paralyze their insect prey, it is not medically significant for people. A bite, which is rare and occurs only if threatened, typically results in nothing more than minor, localized discomfort.
A female Darwin’s bark spider has a distinctive appearance with a black body adorned with white hairs on its cephalothorax, abdomen, and legs. One of her most unique physical traits is the presence of two pairs of humps on her cephalothorax, which distinguishes her from the smaller male.
The web of a Darwin’s bark spider is the largest orb web of any known spider. The entire web structure can be enormous, with some recorded as large as 28,000 square centimeters. The circular orb portion alone can span more than three feet wide, often stretching across entire rivers.
Darwin’s bark spiders primarily eat flying insects that live near or emerge from water. Their diet consists mainly of aquatic insects like mayflies, which they capture by building their massive webs directly over rivers and streams. This specialized hunting strategy is tied directly to their unique habitat choice.
Dr. James Watuwa on May 27, 2019.
Spider Team
