Spiny Orb-Weaver, Spinybacked Orb-Weaver, Crab Spider, Crab-like Spiny Orb-Weaver
Gasteracantha cancriformis
Family Araneidae (Orb-Weavers), Order Araneae. Key family characteristics include building vertical wheel-like webs, possessing eight similar eyes, and utilizing viscid silk for prey capture.
Physical Description
The body features a distinctively wide, flattened, and rigid abdomen equipped with six prominent, sharp spines along the margins. The cephalothorax is dark and compact. Females exhibit dramatic sexual dimorphism, being much larger and brightly colored with hardened, spiny shells, while males are tiny, elongate, soft-bodied, and lack the characteristic spines.
Size Estimate
Females typically have a body width (including spines) ranging from 10 to 13 mm, and a length of 5 to 9 mm. Males are much smaller, measuring only 2 to 3 mm in length. Leg span is proportionally short for an orb-weaver, roughly 20 to 25 mm total across.
Coloration & Markings
The dorsal abdomen typically has a white or yellow background accented with contrasting black spots or markings and dark spines. Color morphs vary widely across regions, featuring white, yellow, orange, or even reddish backgrounds, while the ventral side is usually dark with distinct spotting.
Web Type
Constructs a vertical, traditional orb web characterized by a distinctive open hub and heavy white silk decorations or stabilimenta tufts placed near the center or along the frame lines.
Eye Arrangement
Arranged in two rows of four eyes each on a distinct cephalic tubercle, typical of the orb-weaver family Araneidae, with lateral eyes often grouped in pairs.
Leg Characteristics
Legs are relatively short, stout, and dark, held close to the body, lacking conspicuous spination compared to wandering spiders, specialized for gripping silk rather than fast ground running.
Venom & Safety Information
Venom Information
Possesses mild neurotoxic venom used strictly to subdue small insect prey. It holds no medical significance to humans.
Medical Significance
Harmless to humans. Bites are extremely rare, usually only occurring if the spider is squeezed directly against the skin, resulting in mild, localized pain and minor redness similar to a mosquito bite.
Safety Recommendations
No special precautions needed. Simply enjoy observing them in the garden. If one is found inside a house, it can be safely relocated outdoors using a cup and a piece of paper.
Habitat & Behavior
Habitat & Range
Found widely across the Americas, ranging from the southern United States through Central America down to South America, as well as parts of the Caribbean. Preferred habitats include forest edges, gardens, citrus groves, and shrublands.
Behavior & Temperament
Docile and completely non-aggressive. They remain stationary at the center of their orb webs day and night, waiting for flying prey to impact the sticky spirals.
Diet & Prey
Primarily feeds on small flying insects such as flies, mosquitoes, moths, beetles, and small wasps that become entangled in the vertical orb web.
Seasonal Activity
Most commonly observed during late summer and autumn when females reach full adult size and construct their prominent webs.
Description
The Spiny Orb-Weaver is one of the most recognizable and visually striking spiders in the garden. With its hard, crab-like, brightly colored shell adorned with intimidating spikes, it looks like a tiny piece of living art suspended in a wheel-shaped web. Despite its formidable appearance, it is a gentle and highly beneficial garden resident.
Key Features
Wide, rigid, crab-like abdomen equipped with six distinct marginal spines, paired with bright white or yellow coloration marked by dark spots.
Similar Species
Other members of the genus Gasteracantha found globally, though their geographic ranges rarely overlap. In North America, its unique spiny abdomen prevents confusion with most other common orb-weavers.
Life Cycle
Females produce a cottony, yellowish egg sac deposited on the underside of leaves or twigs near the web, containing hundreds of eggs. Spiderlings hatch in spring, disperse via ballooning, and go through multiple molts, with adults typically active seasonally before dying off in winter.
Ecological Importance
Acts as an effective natural pest control agent in gardens and agricultural settings by consuming large numbers of flying insect pests.
Conservation Status
Not evaluated by the IUCN, but populations are stable, widespread, and common across their native range.
Interesting Facts
The hard, spined shell acts as a brilliant evolutionary defense mechanism, making the spider extremely difficult and painful for small birds and predatory insects to swallow.
Photography Tips
Use a macro lens at a close distance. The best shots capture the spider from directly overhead to showcase the symmetrical spine placement and dorsal patterns against a clean, uncluttered background.
Identified: 2026-08-23T22:41:56.246279