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By Veronica Godines
Geographic Range
The range of the Araneus diadematus extends from New England and adjacent Canada across the northern states to Washington, Oregon, and British Columbia (Kaston 1972).
Habitat
Araneus diadematus live mostly in grassland and require some form of moisture. The environment must provide plenty of attachment sites for the scaffolding of the web; there must be sufficient vertical open space for the orb web (Wise 1993).
Terrestrial Biomes:
savanna or grassland 
.
Physical Description
The female Araneus diadematus has a length of 6.5 to 20 mm, whereas the male is 5.5 to 13 mm. The general color ranges from a pale yellow brown to nearly black. The folium is not as distinct in some of the other Aranea species, and it includes a number of white or yellow spots. The largest of the spots are arranged longitudinally near the anterior end. Usually, there is a pair of white spots at right angles to the longitudinal ones, which gives the group the form of a cross. The cross arangement of the spots is more apparent in the darker varieties, and are caused by guanine cells which shine through the transparent cuticle. The carapace has a median and marginal dark bands. There are four pairs of legs which fan out radially from the connecting carapace and sternum. Each leg has seven segments: a coxa and a trochanter, which are both short; a long femur and a kneelike patella; a slender tibia and metatarsus; and finally a tarsus with three claws. The first pair of the front legs are relatively long and used as feelers for probing the environment. Sensory hairs densely cover the distal leg segments. The external sex organs of the male and female can be seen on the ventral view. Both the male and female's genital openings lie inside the epigastric furrow, except that the epigynum is situated in front of the female furrow. The male also contains a bulb of palp used for the storage of sperm (Foelix 1982; Kaston 1978).
Reproduction
The internal reproductive organs of the Araneus diadematus resembles those of other arthopods. The female's paired ovaries lie in the abdomen and join to form a common oviduct which ends in the uterus and opens to the outside in the epigastric furrow. The female also contains a pair of spermathacae or seminal receptacles. Sperm taken in during copulation are stored here until egg-laying. In males, a common duct is formed by a pair of coiled testes in the abdomen and opens to the exterior at the centre of the epigastric furrow. The males exude their sperm through the epigastric furrow onto a sperm web and transfer it to their palps. The terminal palpal organ is the sperm reservoir and carries out insemination through a narrow tube known as the embolus. The palpal organ serves as a pipette which can suck up and release seminal fluid.
The blood pressure within the male palp increases so that sclerotized projections such as hooks and spines elevate into position to grasp on to the surface of the epigyne. Only the correct palp will fit into the appropriate epigyne. This ensures the successful mating of mating only between individuals of the same species. The males search for a female and are rather cautious when approaching a female, becuase they always risk being dealt with as prey. The male embraces the female's abdomen during copulation and inserts one bulb. Afterwards, the male leaves and his palps are refilled with sperm. This process may only be repeated a few times since the life expectancy of the male is shorter than that of the female.
Before the female starts making her egg sac, she withdraws for several days into her retreat. She then spins a thin layer of single tightly woven silk threads. The first layer is molded by her abdominal movements into a disk known as a basal plate. Then she crawls underneath the basal plate and continuously turns around in circles spinning the cylindrical wall. The palps are held in contact with one side of this wall while spinnerets are placed on the opposite wall. After about two hours, the cylindrical wall grows to 5 mm in height. The cocoon size is directly related to the size of the spider, but not necessarily with the number of eggs it will hold. The female waits for a few minutes and begins to lay her eggs and cover them in a tight pack of silk threads. This becomes the cover plate in which the spider keeps adding layers of thread. The loop mesh ultimately wraps around the entire surface of the egg sac. The female will remain close to the cocoon for the next few days in case the threads need repairing. The female dies a few days after the egg sac is built. The cocoon will appear unchanged externally, while the spiderlings develop internally for a few months. The offspring will emerge in spring, and they will release fine threads of silk from their spinnerets to be carried off by the wind to new locations. Their journey through the air is called ballooning. Wherever each spider drops from the sky will be where its new life begins (Dewey 1993; Foelix 1982; Preston-Mafhan 1996).
Behavior
Araneus diadematus integrates information by the central nervous system and in the visual system of salticids. A spider will adjust its long body axis to be perpendicular to the path of a moving object in order to view the object with the main eyes. Input from the secondary eyes causes the spider to turn without any visual feedback. However, when a moving object is viewed only by the secondary eyes, a spider will not always turn towards it.
This species rebuilds its web every day so that the capture of their prey is more certain (Foelix, 1982). The amino acid composition of the spider silk is a highly unusual protein. Amino acids with short side-chains make up 50-60% of the total fibroin. Before building a new web the spider eats its old web, thus conserving the silk proteins of the spider web (Foelix 1982).
The web of Araneus diadematus usually has 25-30 radial threads forming regular angles of 12-15 degrees. Webs of young individuals often have many more radii than those of adults.
Food Habits
The ultimate purpose of the spider web is to capture prey, and the orb web is the best trap. It is highly geometrical which suggests its special effectiveness and economy as a trap. The hub is slighltly higher than the centre so that the spider may run fast downhill. Therefore the area nearer the hub receives closer spacing of spirals and is coated more densely with sticky globules. Araneus diadematus spends most of its time on the web's hub monitoring the tensions and vibrations in the silk with its sensitive legs. The information regarding the precise position of the arriving insect will instantly be known to the spider. The female Araneus diadematus rests on one side of the web and monitors her web by holding on to a signal thread. When catching prey, Araneus diadematus wraps the prey in silk thread before consuming it. After killing and wrapping the prey, Araneus diadematus does not always consume it immediately. The number of prey attacked and killed is more likely to decrease as the rate of prey supply is increased and the spider becomes satiated (Foelix 1982; Preston-Mafham 1996; Wise 1993).
Economic Importance for Humans: Positive
Araneus diadematus feeds on insects, thus helping to reduce the population of insects in the world. People can put a clean spider's web on a cut or wound to stop the bleeding and help the cut to heal (Foelix 1982; Parsons 1990).
Conservation Status
IUCN Red List: [link]:
Not Evaluated.
US Federal List: [link]:
No special status.
CITES: [link]:
No special status.
State of Michigan List: [link]:
No special status.
There is no special conservation status needed for this species.
Other Comments
Araneus diadematus is a large species and the best known of all orb weavers (Comstock 1980).
Contributors
Veronica Godines (author), Southwestern University.
Stephanie Fabritius (editor), Southwestern University.
