Cross Orbweaver Spider

Araneidae—Orbweavers

(Araneus diadematus)

Araneus diadematus immature. Photo by Steven Jacobs, Penn State Extension

The cross orbweaver was probably introduced from Europe, where it has been studied at some length. While a showy orbweaver, it is commonly encountered on or next to buildings with exterior lighting, including lighted stairwells of structures in more rural settings. It is known from Pennsylvania north throughout New England, throughout Canada, and then south into Washington and Oregon.

Description

Adult females range in length from 6.5 to 20 millimeters, and the males are 5.5 to 13 millimeters long. The color varies greatly from specimen to specimen. Generally, the smaller and/or younger individuals are darker, while the adult females are lighter. The background color is yellow to brown with two wavy or scalloped longitudinal lines (folium). There are several white or yellow spots within and around the folium. Four elongated spots appear toward the anterior end of the abdomen, creating what appears to be a cross. As with the banded garden spider, the carapace has three dark longitudinal lines or bands.

Life History/Behavior

The adults are found from late summer through autumn. In late September, the females leave their webs and seek out protected locations to deposit between 300 to 900 eggs. The eggs are enclosed within a cocoon of yellow, silken threads, shaped in a hemisphere. Typical egg deposition sites include under the bark of dead trees and in cracks and crevices.

Medical Importance

Verified bites by this species are reported to produce a range of symptoms, including pain, swelling, and redness. Systemic reactions include anxiety, nausea, headache, and muscle cramps, but not all individuals have the same reactions. Symptoms/reactions can last from two days to three weeks.

Reference

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Kaston, B. J. 1972. How to Know the Spiders. 3rd ed. Wm. C. Brown Company, Dubuque, Iowa. 272 pp.

Levi, H. W. 1959. "The Spider Genus Latrodectus (Araneae, Theridiidae)." Trans. Amer. Microscopical Soc. 78(1): 7–43.

Long, D., R. Snetsinger, and K. F. Helm. 1995. "Localized Pruritic Rash Due to Recurrent Spider Bites." J. Geriatr. Dermatol. 3(6): 186–190.

McKeown, N., R. S. Vetter, and R. G. Hendrickson. 2014. "Verified spider bites in Oregon (USA) with the intent to assess hobo spider venom toxicity." Toxicon 84: 51–55.