Spiny Orb-Weaver, Spinybacked Orb-Weaver, Crab Spider, Jewel Spider
Gasteracantha cancriformis
Araneidae (Orb-Weavers), Order Araneae. Key family characteristics include building vertical, wheel-like orb webs and possessing eight similar eyes.
Physical Description
Broad, hard, shell-like abdomen that is significantly wider than it is long. The abdomen is adorned with six prominent, sharp, spine-like projections. The cephalothorax is small and tucked underneath, and legs are relatively short and stout.
Size Estimate
Females range from 5 to 9 mm in body length and 10 to 13 mm in width. Males are much smaller, around 2 to 3 mm. This specimen is an adult female.
Coloration & Markings
Bright white or pale yellowish-green dorsal abdomen with distinct black spots arranged symmetrically. The six spines are dark black or reddish. The ventral side and legs are dark brown to black.
Web Type
Vertical orb web featuring a sticky spiral for catching flying insects, typically constructed between shrubs or low tree branches.
Eye Arrangement
Eight eyes arranged in two rows of four, typical of the orb-weaver family Araneidae, with lateral eyes situated on small tubercles.
Leg Characteristics
Short, relatively stout legs colored black or dark brown, equipped with specialized claws for manipulating silk and navigating the orb web without getting stuck.
Venom & Safety Information
Venom Information
Contains mild neurotoxins designed for subduing small insect prey. It is not potent or dangerous to humans.
Medical Significance
Harmless to humans. Bites are extremely rare, generally only occurring if the spider is squeezed directly against the skin, resulting in mild local pain and slight swelling that resolves quickly without medical intervention.
Safety Recommendations
No special precautions needed. Enjoy observing them in your garden. If one wanders indoors, simply scoop it up gently in a container and release it outdoors.
Habitat & Behavior
Habitat & Range
Found throughout the Americas, from the southern United States through Central America and into South America, as well as the Caribbean. Prefers forest edges, scrublands, and residential gardens.
Behavior & Temperament
Docile and non-aggressive. They remain stationary in the center of their webs day and night, waiting for prey, and will drop to the ground or retreat if severely disturbed.
Diet & Prey
Small flying insects such as flies, mosquitoes, moths, and small beetles captured via the vertical orb web.
Seasonal Activity
Active primarily from spring through autumn, with mating occurring in the warmer months and adults often dying off with the onset of winter frost after laying eggs.
Description
The Spiny Orb-Weaver is an architectural marvel of the spider world, easily recognized by its brightly colored, crab-like, spiny abdomen. Hanging motionless in the center of its vertical wheel web, it resembles a colorful geometric jewel or a tiny floating crustacean rather than a traditional spider. Perfectly harmless to humans, these beneficial arachnids serve as vigilant guardians against garden pests.
Key Features
Wide, flattened, shell-like abdomen equipped with six distinct marginal spines and a striking pattern of black spots on a white or yellow background.
Similar Species
Other members of the genus Gasteracantha found globally, though their geographic ranges rarely overlap with Gasteracantha cancriformis.
Life Cycle
Females produce a silken egg sac containing hundreds of eggs, attached to the underside of a leaf. Spiderlings hatch, disperse via ballooning, and mature through multiple molts over a single season.
Ecological Importance
Acts as a natural predator and pest controller by consuming large quantities of flying insects in gardens and natural habitats.
Conservation Status
Not evaluated by the IUCN, but populations are stable, widespread, and common throughout their natural range.
Interesting Facts
Despite their fierce, crab-like appearance and spiny armor designed to deter bird predators, they are completely harmless to humans. Their hard shell is actually a hardened exoskeleton.
Photography Tips
Use a macro lens to capture the fine details of the abdominal spines and spot patterns. A neutral background like foliage works best, and early morning light provides soft illumination without harsh shadows.
Identified: 2026-08-22T19:50:05.426118