Steatoda bipunctata

Fat spider ( Steatoda bipunctata ) ( female)

The fat spider ( Steatoda bipunctata ) is a spider species of the same genus of the fat spiders of the family of cobweb spiders. It is Holarctic distribution and is in Central Europe, especially in buildings where they like to build their webs in dark corners. The largest specimens reach a body length of 8 mm (without legs), in the majority of cases, the animals are, however, much smaller.

Description

Steatoda bipunctata is reddish in color and sometimes brown. Her body is a fatty luster, whence probably the result of the name. On the back of the abdomen, it has two times brighter that develop with advancing age to two broad stripes in females. A bright, white to pale yellow ring extends from the petiole at the sides to the middle of the abdomen. On the ventral side of the opisthosoma is a bright spot is in the field of epigynum. He is flanked by bright line, which converge like a horseshoe pulled up above the spinnerets. The spinnerets are usually seen clearly, but facing down. The legs are indistinctly striped red and brown. A dense pubescence is revealed under the microscope.

Way of life

Your on the glance invisible or appearing confused networks build the predominantly nocturnal, very shy animals in dark corners of buildings, in the open air near the ground under stones or in crevices. The three-dimensional network of about 10 cc size condenses into a dense matting, which is woven in a few centimeters in height between tension cables. The tension cables run in diagonal- vertical direction and tighten the mat in all directions. These fortifications often branch out once or twice, so that the load is distributed to various adhesive dots. This tension cables are used to yield catching females of S. bipunctata at the same time as stumbling threads. Runs into prey, they will be lifted up to the tensioned strings and hangs there. They are thus able to overpower prey that are much larger than themselves, the fat spider will - unless they hanging upside down in the net during their active hours - alerted by alarm threads, which are clamped to the retreat. In this retreat, which is a living space of only a few millimeters wide, like a wall or rock crevice or a cavity of a window hinge, she withdraws during the bright hours of the day and hides it in potential danger by larger animals by mainly vibrations are perceived. If the loot drops from the top of the net, it must partially into bite even holes. The prey is wrapped but not stunned, and sucked in later stages. The leftovers are then removed from the mat and simply dropped.

S. bipunctata withstands drought and can be measured on their body size to accommodate dewdrops or to cause drops of considerable amounts of water, so that they can grow old in human dwellings. At higher population density similar neighbors are tolerated and the networks connected to each other, but the biggest female retains the best and largest squares, which can lead to the migration of the neighbors.

Reproduction

The males usually wander around. The network is used for courtship also the communication by plucking and for weaving various elements of unknown function by the male; possibly is sperm balls. The male loses weight as it weaves amazing amounts of communication threads, before it has found the power of the female, after days of searching.

The males of the species possess stridulating organs. With them, they generate a ( according to the literature for humans slightly audible ) three coated Cis of 1000 Hz males stridulate also contact each other when they compete for a female. The stridulation is rocked quickly with the opisthosoma, with strong spines of the opisthosoma be deleted on ridged skin surfaces on the prosoma. The pairing willing females then starts their search and responds with drums and paddles on the net. A trigger for the mating behavior include chemical substances that are contained in the female silk.

At sheltered sites in the female animals are active year-round. The courtship takes place in the summer, which can take several days to weeks. The females mated also with two males. The males ( one each ) live during courtship and even after mating with the females extended period of time together in the female network. The successful male will there leave something of the prey, they also may obtain the Retrait the wife, with the females, however, the Lauerstellung reserves to signal threads in their Tarsalklauen.