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!
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.
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.
A female Spinybacked Orbweaver is identified by her six prominent abdominal spines and distinct coloration. She measures 0.20 to 0.35 inches and has a white or yellow upper abdomen with black or red spines. Her underside, legs, and carapace are black with characteristic white spots.
Spinybacked Orbweavers are not considered dangerous to humans. While they possess venom to subdue insect prey, it is not medically significant for people. They are non-aggressive and bites are very rare, typically only occurring if the spider is pressed directly against the skin and feels threatened.
Spinybacked Orbweavers show a notable size difference between sexes. Adult females are larger, measuring between 0.20 and 0.35 inches (5 to 9 mm) in length, not including their legs. Males are significantly smaller and less conspicuous, making them much less frequently observed than the females.
Spinybacked Orbweavers display variable coloration, primarily on their abdomens. The upper side can be white or yellow, with contrasting red or black spines. The carapace, legs, and underside are typically black with white spots. Males usually have a less vibrant, grayish abdomen also marked with white spots.
Male and female Spinybacked Orbweavers differ in size, color, and spine count. Females are larger with bright white or yellow abdomens and six prominent spines. Males are much smaller, have a dull grayish abdomen with white spots, and possess only four or five reduced abdominal projections.
Spinybacked Orbweaver eggs are protected within a distinctive egg sac. The female lays her eggs on a silk sheet and then wraps them securely in yellowish or white silken strands. The eggs hatch in about 13 days, revealing tiny, pinkish-white spiderlings just before their first molt.
A female Spinybacked Orbweaver builds a new web each night to ensure it is strong and sticky for capturing prey. The daily reconstruction replaces any damage from wind, debris, or previous captures. The spider then sits in the center, facing down, waiting for insects to become ensnared.
Dr. James Watuwa on June 29, 2019.
Spider Team
