Araneidae

These are the orb weaver spiders: they spin webs in the form of an orb. Some adults remain at the center of the orb, while others build a retreataway from the web. In many species there is considerable sexual dimorphism; the males are often smaller and have a different-shaped abdomen than the female.

Araneus cornutus (Fig. 18.6h) Males are 7-9 mm long and females are 9-12 mm long. The carapace is brown to gray. The abdomen has a distinct scalloped pattern, which is grayish brown, with pale areas within, and dark brown to black at the sides. Webs are built on low bushes, bridges, and around the outside of buildings. This species occurs in the USA, from New England south to North Carolina and west to Oklahoma and Nebraska.

Black and yellow garden spider, Argiope aurantia (Fig. 18.6b)

Males are 5-8 mm long and females are 19-28 mm long. The carapace is usually covered with white or silvery-white setae. The abdomen is marked with black and bright yellow, or orange; it is slightly pointed posteriorly and curved at the sides to form a hump on each side. The front legs are entirely black; others have reddish-brown or yellow femora and the other segments black. Webs are constructed on vegetation, tall grass, and around houses (near outdoor lights). They usually occur in locations such as on porches or garden furniture. Webs often contain a zigzag stabilmentum of thick silk, which extends above and below the center of the web. The egg-sacs are light-brown spheres, 20-25 mm in diameter. This species occurs throughout USA.

Banded garden spider, Argiope trifasciata (Fig. 18.6c) Males are 4-5 mm long and females are 15-25 mm long. The carapace and abdomen are pale yellow with a thick covering of silver and white setae. Legs are pale yellow, and the femora and front legs may be entirely black. The abdomen is marked with black bands; the legs are spotted. The tip of the abdomen is somewhat pointed; the anterior margin lacks the notch and humps that characterize A. argiope. This species is generally distributed in the USA; adults are common in early September.

St. Andrews cross spider, Argiope keyserlingii Males are 5-6 mm long and females are 10-15 mm long. The cephalothorax is brown, and the abdomen is striped yellow and brown. The stabilmentum in its web is the shape of a cross. This species occurs around the outside ofbuildings in Australia.

Metepeira globosa Females are about 8 mm long. The cephalothorax is brownish yellow with a dark longitudinal median line. The abdomen is oval with four pale yellow or pink spots that are partly united into a rectangular mark and surrounded by a black line. Legs are banded in both sexes. Webs are usually a composite of a vertical orb and an irregular and unstructured web that extends from the top of the orb, covering about half of it. There is a strong thread extending to the center of the orb. This species occurs in the USA.

Neoscona domiciliorum Males are 6-8 mm long and females are 10-12 mm long. The abdomen is shaped slightly triangular; markings are yellow and brown, paired with black spots. Tibia 2ofthemaleisstraightwith strong setae. This species occurs in open woods, on fences, and around buildings. Itis distributed throughout the USA.

Neoscona nautica Males are 6-7 mm long and females are 8-12 mm long. The cephalothoraxis greenish brown to yellowish brown. The abdomen is enlarged and slightly triangular; markings are yellowish brown and brown, paired with black spots. Legs are yellowish brown with dark brown tarsi. This species is distributed in Japan.

Nook spider, Zygiella x-notata (= Zilla litterata) Adults are about 10 mm long. The cephalothorax is yellowish brown and has a broad, yellow wedge-shaped stripe. Webs are often constructed in the corner of a window, doorframe, or post. The orb is incomplete and usually a small section remains open; through this section is a single thread that extends to the retreat. This species is distributed in continental USA and Europe. A closely related species, Z. atrica, occurs on the outside of houses.

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