Leslie J. Mehrhoff, University of Connecticut, Bugwood.org
The genus Araneus has about 1,500 species worldwide, making it the largest of all the spider genera. Araneus marmoreus is found throughout all of Canada to Alaska, the northern Rockies, from North Dakota to Texas, and then east to the Atlantic.
Adult female marbled orbweavers are 9 to 20 millimeters in length with very large abdomens that are mostly orange with brown to purple markings and spots of pale yellow. Occasionally the abdomens are nearly white in color. The cephalothorax is yellow to burnt-orange with a central dark line and dark lines down either side. The femora and patellae are orange. The other leg segments are yellow, becoming brown at the distal ends, as are all of the legs of the males.
The webs are found in trees, shrubs and tall weeds, and grasses in moist, wooded settings and can frequently be found along the banks of streams. The webs are oriented vertically and have a “signal” thread attached to the center that notifies the spider when prey has been captured. Unlike the Argiope garden spiders, Araneus marmoreus hides in a silken retreat to the side of the web (at the end of the signal thread). Adults construct this retreat using leaves folded over and held together with silk. Immature spiders make their retreats out of silk only.
Egg sacs, which contain several hundred eggs, are generally deposited in October and are constructed of white silk formed in a flattened sphere. Immature spiders emerge from the sacs in spring. Adults are seen from mid-summer until the first hard freeze of fall.
It is unlikely that bites would occur unless people handled a female with an egg sac in the web. Even then, the bite would likely cause no more discomfort than a wasp or bee sting in most individuals.
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