The female Araneus gemma measures 0.39 to 0.47 inches (10 to 12mm). Its carapace and abdomen are variable in color from gray to brownish purple. The abdomen has anterior paired humps and may have a medial light stripe that varies in length. The male is smaller than the female, measuring 0.24 to 0.31 inches (6 to 8 mm). It is similar in color and pattern to the female.
Araneus gemma ranges along the West coast of North America from southern Alaska to southern California and inland to western Montana. It can be found in coastal San Diego County. Webs are built in open areas of trees, large shrubs and around dwellings.
This species matures and is most often seen in the fall. It is not dangerous to humans.
Related and Similar Species
Araneus andrewsi has a mottled brown abdomen and usually does not have the medial brown stripe on the abdomen. Neoscona crucifera is more orange-brown, has no abdominal medial stripe and no paired humps.
Levi, H.W. 1971. The diadematus group of the orb-weaver genus Araneus north of Mexico (Araneae: Araneidae). Bull. Mus. Comp. Zool. 141(4):131-179.