Araneus cavaticus

Araneus cavaticus
	Araneus cavaticus , female
Systematics
Class :	Arachnids (arachnida)
Order :	Spiders (Araneae)
Subordination :	Real spiders (Araneomorphae)
Family :	Real orb web spiders (Araneidae)
Genre :	Garden spiders ( Araneus )
Type :	Araneus cavaticus
Scientific name
	Araneus cavaticus
	( Keyserling , 1881)

The spider species Araneus cavaticus is a North American representative of the genus cross spiders ( Araneus ). Usually the up to 22 millimeter long spider is yellow to dark brown in color. In English the spider is called the common barn spider . At this name they came (because of their frequent occurrence in barns English barns , sheds or similar wooden structures). The spider became popular as "Charlotte" in the children's book Wilbur and Charlotte (1952) by Elwyn Brooks White (1899–1985).

features

The males of the spider species Araneus cavaticus reach a body length of about 6 to 7 millimeters, the females are significantly larger with 13 to 22 millimeters. The carapace is yellow-brown in color, slightly lighter in the male than in the female. The abdomen (opisthosoma) is dorsally tinged pale yellow to gray-brown and has a dark brown zigzag pattern along the midline (median line). Ventrally , it is black between the sex organ ( epigyne ) and the spinning glands . Due to their color, they are well camouflaged in the vegetation and therefore difficult to spot. In both sexes there are two small, white, clearly recognizable spots on the ventral abdomen. The legs have sparse hairs with short white hairs. In the female, the legs are pale yellow to yellowish brown with dark brown bands.

distribution and habitat

Araneus cavaticus is distributed over the eastern third of North America from Canada to Texas . They are mainly found in late summer and autumn. They often populate barns, sheds and similar wooden structures in rural and suburban areas with abundant tree and shrub growth, but also caves, mines and rock overhangs as well as boats near lakes.

Lifestyle and diet

Araneus cavaticus is very aggressive towards other spiders . In particular, it shows a pronounced territorial behavior and attacks other spiders.

Net construction is almost always based on a long bridge thread that she has stretched, for example, between two tree branches or the corners of a barn. This can be a length of five meters and runs diagonally from top to bottom. The finished wheel net consists of about 20 catch threads and usually has a diameter of about 50 centimeters. It is regularly constructed with symmetrical spoke threads, whereby the distance between the catch threads decreases significantly from the outside to the inside: while the outer catch threads are ten to twelve millimeters apart, the inside is less than two millimeters. Since the spider is nocturnal, it sits on one of the ends of the bridge thread during the day. She usually rebuilds her net every day, reusing silk from the previous net.

Araneus cavaticus feeds on insects that it prey on with its net. At night the spider waits in the middle of the web for a prey to get caught in the web. When the tissue vibrates, it shakes and swings the relevant threads in order to recognize whether it is really prey and not, for example, dirt particles or leaves. In this way it can also obtain information about the size of the object. If it is a prey animal, she quickly grabs it and immediately weaves the victim with silk. Then she is injected with a toxin and a digestive enzyme through a bite and sucked out shortly afterwards.

Reproduction

Araneus cavaticus reaches sexual maturity in the second year of life. The male then no longer builds his own net, but stores spermatophores on the last net. With that, the male goes in search of a female. It checks their willingness to mate by tugging at their net. When the female is ready to mate, both partners slowly approach. If the female turns on her stomach, the male jumps up and passes the sperm packets into the sperm sac with the mating organs ( embolus ) on the pedipalps. Copulation only takes a few seconds. Since the male runs the risk of being eaten by the female after mating, it quickly moves away from the net.

A few weeks after mating, the eggs are laid in a small spun cocoon, where they overwinter. The young spiders hatch in spring. They also feed predatory on micro-insects.

toxicity

A defensive bite from Araneus cavaticus can only occur in close, hopeless threats . In mammals and humans, local irritation and reddening of the skin can occur, which can be compared to a bee sting. The bite, which is hardly poisonous for humans, should be cleaned and treated like an ordinary insect bite and a doctor should be consulted if allergic symptoms occur.

Danger

The species occurs frequently in its range and is not endangered.

gallery

Females spinning their prey
Males from below
Females in their net

Pop Culture

As "Charlotte" the spider became popular in the children's book Wilbur and Charlotte (orig. Charlotte's Web ; 1952) by Elwyn Brooks White (1899-1985). What is interesting about this is the full naming of the character as "Charlotte A. Cavatica", which alludes to the scientific name of the spider Araneus cavaticus . One of Charlotte's daughters called herself “Aranea” when she asked for the middle initial of her mother's name, who had died before hatching.

The animated musical Charlotte's Web (German title: Zuckermanns Farm - Wilbur im Glück ) by Hanna-Barbera from 1973 is based on this children's book. 30 years later, the sequel Charlotte's Web 2: Wilbur's Great Adventure (German title: Schweinchen Wilbur's great Adventure ), which was produced directly for the video or DVD market. In 2006, the US feature film Charlotte's Web (German title: Piggy Wilbur and his friends ) came out.

Ultimately, in 2006/07 the video game Charlotte's Web (German title: Schweinchen Wilbur und seine Freunde ) for Microsoft Windows , Game Boy Advance , Nintendo DS and PlayStation 2 , which is an adaptation of the feature film and is for players between the ages of 4 and 7, followed Years ago.

literature

Herbert W. Levi: The diadematus group of the orb-weaver genus Araneus north of Mexico (Araneae: Araneidae) . In: Bulletin of the Museum of Comparative Zoology . Volume 141, No. 4 . Cambridge 1971, p. 131-179 .
Eugen von Keyserling : New Spiders from America III . In: Negotiations of the Zoological-Botanical Society in Vienna . tape 31 . Vienna 1881, p. 269-314 .