Joro spider

A type of golden orb weaver spider

Basic Information

Anatomy

Adult female jorō spiders are large and brightly colored, with body length up to 1 inch and a leg span up to 4 inches. The dorsum of the prosoma (cephalothorax) is covered with golden or silvery hairs. The opisthosoma (abdomen) is cylindrical, with bright yellow with grey-blue bands on the dorsum and an intricate yellow and grey-blue pattern with a large red mark on the venter. The legs are black with yellow bands. Adult male jorō spiders are much smaller and duller in color compared to females, with a body length of only 0.3 inches (Figure 3). The prosoma is light brown with lateral dark brown stripes and the opisthosoma has a dark brown central stripe.

Growth Rate & Stages

Jorō spiders overwinter as eggs in a papery silk egg sac. Spiderlings emerge in early summer and usually go relatively unnoticed. While small, they can be transported through the air through a process called ballooning, where the young spiders release silk and are picked up by the wind. Ballooning spiderlings can travel tens to hundreds of miles, especially if they are picked up by strong winds and storms. Male spiders mature in late summer and females in early fall. Adult female jorō spiders create large webs that can be up to 10 feet wide. The webs are suspended between two or more objects, such as trees, bushes, light or fence posts, etc. Adult male spiders do not spin their own webs but are found in the webs of females. Female spiders lay a single egg sac which contains 400–500 eggs, which is usually attached to bark, leaves, or human structures.

Genetic Descendants