Joro Spider

• The males are tiny compared with the females: barely a quarter of their length.
• Its young disperse by ballooning, releasing threads of silk into the wind to travel for kilometres, which explains how fast it has spread across North America.
• Despite the media alarm that accompanied its arrival in the United States, its bite is harmless to people and rarely even breaks the skin.
• It is a recent and highly visible invader: it was detected in Georgia, in the United States, around 2014, probably arriving in a container from East Asia, and has since spread through several south-eastern states.
• Its northward expansion is put down to its cold tolerance: it has a higher metabolic rate and heart rate than its tropical relatives and survives brief frosts, which opens up much of eastern North America to it.
• Its silk is golden and very strong, and its webs can exceed a metre in diameter.
• It disperses by ballooning: the young release threads of silk that lift them on the wind and carry them for kilometres, which greatly speeds up the invasion.
• It is shy and practically harmless: its chelicerae barely pierce human skin, and when disturbed it stays motionless for a long while.
• Its ecological impact is still being assessed, and so far there is no evidence that it displaces native spiders.

Skeleton type

Invertebrate - chitin exoskeleton (arachnid)

Habitat & environment

Forest edges, gardens and suburban areas

Sources consulted: Davis y Frick (2022), Physiological Entomology; Universidad de Georgia; Hoebeke et al. (2015), PeerJ

Best time: Late summer and autumn, when the females reach their full size