Spinybacked Orbweaver (Gasteracantha cancriformis)

Discover the spiny-backed orb-weaver, a fascinating spider from the orb-weaver family. Found mostly in the New World, these spiders are known for the unique, spine-like bumps on their back. In this post, we’ll share some cool facts about them!

Scientific Classification

• Family: Araneidae
• Genus: Gasteracantha
• Scientific name: Gasteracantha cancriformis

Physical Description and Identification

Adults

• Size: Females are 0.20 – 0.35 inches (0.5 – 0.88 cm) while males are smaller, measuring 0.39–0.51 inches (0.99 – 1.2 cm)

• Color: The underside, legs, and carapace appear black, with white spots marked on the abdomen. The upper side of the abdomen could be white or yellow, and the color of the spines would vary accordingly. The white upperside would have black or red spines, whereas, in the case of the yellow variation it would be just black. The coloration mentioned above is mostly seen in females, while the male species have a grayish abdomen, spotted in white.

• Other Characteristic Features: The females have six abdominal projections, while in males it is reduced to four or five.

Eggs

The eggs after being laid on a silken sheet are wrapped in yellowish or white silken strands. They hatch within 13 days and have a pinkish-white coloration just before their first molt.

Spiderlings

At the onset they appear bright and within 5 or 7 days become darker. The spiderlings usually emerge during the winter and disperse on their own in the following spring as they gain sexual maturity.

The Web

Female spiders make webs every night using silken strands, and then sit on it facing downwards waiting for their prey. The males hang from a single thread near the web to allure females.

Are Spinybacked Orbweaver Spiders Venomous?

Yes, spinybacked orbweaver spiders have venom, but it’s usually not harmful to humans and is used to subdue their prey.

Can Spinybacked Orbweaver Spiders Bite?

Spinybacked orbweaver spiders can bite if threatened, but their bite is generally not dangerous to humans and might cause mild irritation.

Ecological Importance and Behavior of Spinybacked Orbweaver

The spiny-backed orb-weaver plays a crucial role in maintaining ecological balance, primarily through its diet consisting of moths, whiteflies, beetles, and drosophilids. Their nocturnal web-spinning activities contribute to the control of insect populations in their habitats.

Natural Predators and Prey-Predator Dynamics: Birds and larger insects stand as natural predators to the spiny-backed orb-weaver. The spider’s survival hinges on its ability to expertly navigate these predator-prey dynamics, utilizing its web both as a tool for capturing prey and as a means of evasion from predators.

Relationship with Humans: Commonly found in shrubby gardens, woodland edges, and trees, the spiny-backed orb-weaver is a familiar sight to many. Despite its venomous nature, it poses little to no threat to humans, instead serving as a natural pest controller.

Quick Facts

Other Names	Spinybacked orb weaver, star spider
Distribution	United States, Cuba, Jamaica
Habitat	Shrubby gardens, woodland edges, trees
Diet	Moths, whiteflies, beetles, and drosophilids
Web Type	Orb web
Predator	Whiteflies, beetles, flies, moths
Lifespan	Maximum 1 year
IUCN Conservation Status	Not listed

Did You Know

• Gasteracantha, its genus name comes from the Greek words “gaster” meaning belly, and “acanthi” which translates to thorn. The scientific name is an amalgamation of two Latin words “cancer” meaning crab and “forma” referring to shape.

In summary, the spiny-backed orb-weaver spider stands as a testament to the intricate beauty and complexity of the natural world.

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