Joro Spider, Joro-gumo
Trichonephila clavata
Araneidae (Orb-Weavers), Order Araneae. Key family characteristics include building vertical, wheel-like orb webs, having eight similar-sized eyes, and lacking specialized cribella.
Physical Description
The Joro Spider features an elongated, cylindrical abdomen and a distinctively patterned cephalothorax. Females exhibit striking sexual dimorphism, growing significantly larger than males with bold coloration. The body is relatively smooth with fine, short hairs.
Size Estimate
Females have a body length of 17-25 mm and a leg span reaching up to 70-100 mm (roughly the size of the palm of an adult human hand). This appears to be a mature adult female specimen.
Coloration & Markings
Females feature vivid yellow and dark blue-black transverse bands across the elongated abdomen, often with subtle red or orange tints near the rear. The legs are dramatically banded in black and bright yellow.
Web Type
Builds a large, permanent, three-dimensional orb web spun from strong golden silk. The web often features a characteristic golden sheen that glints in the sunlight and is typically constructed between trees, shrubs, or structural overhangs.
Eye Arrangement
Consists of eight small eyes arranged in two rows on a raised ocular tubercle, typical of the orb-weaver family, aiding in the perception of movement rather than sharp imaging.
Leg Characteristics
Long, slender legs bearing prominent black and yellow or yellowish-white banding. The legs often feature distinct tufts of bristles (often called 'leg brushes') along the tibia and metatarsus, held flat against surfaces or the web.
Venom & Safety Information
Venom Information
Contains a mild neurotoxin primarily used to immobilize insect prey. It is not considered dangerous or medically significant to humans or large pets.
Medical Significance
Harmless to humans. A bite, which is extremely rare and only occurs if the spider is directly squeezed or trapped against the skin, typically causes mild, localized pain and minor redness similar to a mosquito bite.
Safety Recommendations
No special precautions needed beyond standard caution. If found indoors, they can be gently relocated outside using a cup and a piece of paper. No professional pest control is necessary.
Habitat & Behavior
Habitat & Range
Native to East Asia (Japan, Korea, Taiwan, China), but recently established as an invasive species in the southeastern United States (primarily Georgia and surrounding states). Prefers wooded areas, forests, gardens, and human-made structures.
Behavior & Temperament
Docile and non-aggressive. They spend most of their time stationary at the center of their large webs. When disturbed, they typically retreat to the edge of the web or drop to the ground rather than bite.
Diet & Prey
Generalist predators feeding primarily on flying insects such as mosquitoes, flies, stink bugs, and grasshoppers caught in their strong silk webs.
Seasonal Activity
Most active and visible during the late summer and early autumn when females reach full maturity and construct their largest webs. They overwinter in the egg stage.
Description
The Joro Spider is a striking orb-weaver known for its vibrant yellow and blue-black coloration and impressive golden webs. Recently introduced to North America, it has captured public attention due to its size and unique aesthetics, serving as an effective predator of invasive pests like the brown marmorated stink bug.
Key Features
Elongated cylindrical abdomen with bright yellow and dark blue/black bands, strikingly banded yellow-and-black legs, and the construction of a distinctively large golden silk orb web.
Similar Species
The Yellow Garden Spider (Argiope aurantia) and the Silver Argiope (Argiope argentata). Joro spiders are distinguished by their uniquely elongated abdomen, distinct blue-black transverse striping, and bright yellow leg bands.
Life Cycle
Females lay egg sacs containing several hundred eggs in late autumn hidden beneath bark or crevices. Spiderlings emerge in spring, disperse via ballooning, molt multiple times throughout summer, and reach maturity by late summer.
Ecological Importance
Acts as a beneficial generalist predator helping to control nuisance insect populations, including invasive species like the brown marmorated stink bug and spotted lanternfly.
Conservation Status
Not evaluated by the IUCN. Populations are currently stable and expanding rapidly in introduced ranges where they are considered invasive.
Interesting Facts
Joro spiders are famous for 'ballooning,' using silken threads to catch the wind and travel long distances as spiderlings. In Japanese folklore, the 'Jorogumo' is a mythical creature that can transform into a seductive woman.
Photography Tips
Photograph from the side or slightly above to capture the full pattern of the abdomen and leg banding. Use natural backlighting to highlight the golden sheen of the web, and maintain a safe, still distance to avoid disturbing the spider.
Identified: 2026-10-06T23:43:13.224782