Southern black widow
| Southern black widow | ||||||||||||
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Southern black widow, female |
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| Scientific name | ||||||||||||
| Latrodectus mactans | ||||||||||||
| ( Fabricius , 1775) |
The southern black widow ( Latrodectus mactans ), usually just called the black widow , is a spider from the family of canopy web spiders . The species, which is prominent and feared due to the effects of its poison, can be found in the southeastern United States and is also the best-known species of the real widows ( Latrodectus ).
The English trivial names of the southern black widow are Black widow , Southern black widow and Shoe-button spider . While the meaning of the first two English trivial names is identical to that of the two German names, the third translates as "Schuhknopfspinne".
features
The female of the southern black widow reaches a body length of eight to 15 millimeters. This makes the species one of the larger representatives of the genus. The leg span of the female is 25 to 35 millimeters. As with the other true widows, the males are considerably smaller with a body length of only four to seven millimeters and a leg span of 12 to 18 millimeters. As with all true widows ( Latrodectus ), the southern black widow also has a strongly pronounced sexual dimorphism (difference between the sexes) due to further characteristics .
female
The basic color of the female is usually glossy deep black, more rarely dark brown. Their legs, which are longer than the body, are also black. There are also two markings. One of these is the ventral drawing consisting of two fused triangles in the form of an hourglass, which is typical for real widows. The second drawing element is a small red spot above the spinneret . Both markings can also be colored yellow or orange. Otherwise the female has no color elements. Younger females, on the other hand, have a coloring that is similar to that of the males.
male
The contrasting colored male also has a black base color and, unlike the female, a more elongated opisthosoma and a different, mostly yellow mark on the flanks of this section. The male has longer legs than the female and the joints are brown in color. The young are predominantly white or yellowish white. Later they show variable drawings on the upper side of the opisthosoma, mostly red spots that can be outlined in orange or yellow.
Similar species
Similar species can sometimes be found in the genus of the real widows ( Latrodectus ). The female of the southern black widow, for example, can be confused with that of the northern black widow ( Latrodectus variolus ), in which the two triangles on the vertical side are not fused together. Other similar species are the western black widow ( Latrodectus hesperus ) and the native European black widow ( Latrodectus tredecimguttatus ), which is represented in the Paläraktis and previously also counted as a subspecies of the southern black widow and also often referred to as the black widow . It looks very similar in shape and color to the southern black widow, but in the adult stage it usually has thirteen red spots on the abdomen.
The southern black widow can also be confused with individual species of the genus fat spiders ( Steatoda ), which are also counted among the crested web spiders and are also referred to as false widows due to their similarity to the real widows. One example is today in North America by introduction occurring Noble orb spider ( Steatoda nobilis ). A striking distinguishing feature of both genera is the chelicerae (jaw claws) present in the fat spiders and the lack of teeth in the real widows including the southern black widow .
Occurrence
The southern black widow is found in the southeastern states of the United States , from southern New England to Florida and west to eastern Oklahoma , Texas, and Kansas . It is much more common in the southern states than in the northern states. Its southern distribution area extends to Guatemala.
In the north the distribution area overlaps with that of the northern black widow ( Latrodectus variolus ), in the west it borders on that of the western black widow .
The southern black widow has been introduced into some countries through international trade. It has been observed in Hawaii since 1925.
The spider lives in dry, steppe-like areas near the ground between stones and undergrowth, specimens have rarely been found in villages or towns.
Way of life
The southern black widow belongs to the crested web spiders, whose characteristic feature is the comb-like hairiness of the legs. With the help of this fine comb structure, the spider builds its canopy network. The ceiling web, which is created like a hood between grasses or overhanging rock structures, consists of a tangle of short, wide-meshed threads that are held like a tent by tension threads. In the upper part of this web is the bowl-shaped hiding place of the spider. From the hood net, sticky threads are pulled in all directions, which are used to catch insects. The net has a diameter of 30 to 40 centimeters.
The spider mostly feeds on winged insects such as flies , grasshoppers, and beetles . Larger animals that get caught in the net can also be destroyed. Places suitable for network construction are holes in the ground or large rocks and stones, but also piles of wood, sheds or small huts and garages. This also includes outdoor abortions, which attract many insects. However, the black widow also eats other spiders, such as B. trapdoor spiders .
The southern black widow rarely leaves her web. It is nocturnal and during the day hides in its tightly woven hiding place. At night she hangs her back down in the middle of the hood net.
Reproduction
The mating takes place in spring or summer, here the male spins the legs of the female with some threads. Then it inserts the semen into the female's sperm opening. After mating, the male is sometimes eaten, but reports on the frequency of this event have varied. Most scientists describe this behavior as rather rare for the southern black widow.
The female now spins spherical egg cocoons 8 to 14 millimeters in diameter. These are white at first, but can turn brownish to gray over time. There are 25 to 250 eggs in the cocoons. Several egg cocoons can be produced in a year. These are guarded by the female and the female can react particularly aggressively during this time.
The first hatchlings hatch after four weeks. But they still stay in the cocoon, where they moult for the first time. Then they leave the web and float through the air on long threads. They are spread by the wind. The development to the sexually mature animal takes two to four months, depending on the food available.
Often the females only live one year, in favorable cases and in terrariums they can live up to three years.
Bite accidents and toxicity
The southern black widow's bite is not always noticed immediately, it can usually only be felt like a pinprick. The spider injects a nerve poison into the bite wound , which is noticeable after half an hour at the earliest. The clinical observation period after a bite by Latrodectus mactans is therefore at least six hours. The neurotoxin is a mixture of proteins from which more than 20 different latrotoxins have been isolated so far. The main component of the poison is alpha-latrotoxin . It causes involuntary neuromuscular discharges that lead to cramping abdominal pain and, after one to three hours, generalized, rapidly increasing muscle pain that, if left untreated, can last for days. Local swelling and reddening appear on the bite wound.
Humans are rarely at risk of death because of the relatively small amount of venom that is transferred into the wound when bitten. The likelihood of someone dying depends on their health, the elderly and children can die from the bite. Before antiserum treatment was introduced , the death rate after a bite was five percent. Due to its massive occurrence and the resulting frequent bites, this spider has become very well known as a poisonous animal. But it only bites when disturbed or attacked. Only the females are dangerous, the males are harmless.
Names and systematics
The name black widow comes from the observation that the females eat the smaller male after mating. This behavior, which can also be observed in most other species of weaving spider , is, however, rather the exception in the black widow.
The first describer Johan Christian Fabricius placed Latrodectus mactans as Aranea mactans in the genus Aranea in 1775 , in which most of the spiders were grouped at the time. Today the spiders are grouped together to the order Araneae, in which the southern black widow belongs to the family of the crested web spiders (Theridiidae).
In 1970, the black widows of North America were divided into three types by a revision by BJ Kaston: From Latrodectus mactans in the narrower sense, which is mainly distributed in the southeastern states of the USA, and was henceforth called the Southern Black Widow, the variant native to the north as northern black widow ( Latrodectus variolus ) and the western black widow ( Latrodectus hesperus ), which is widespread in the west, separated as separate species.
gallery
Another color variant of a female
Top and bottom of a female
Frontal view of a female
Lateral view of a female
Young male
Sketches on the stages of development of the southern black widow
literature
- G. Schmidt: Poisonous and dangerous arachnids. (= Die Neue Brehm-Bücherei. Volume 608). 2nd Edition. Westarp Sciences, Magdeburg 2000, ISBN 3-740-30249-6 .
Web links
Southern Black Widow in the World Spider Catalog
- Article from Tierdoku.de
- Datasheet at Bugguide (English)
- Venomous Spiders in Florida (English)
Individual evidence
- ↑ a b Steatoda nobilis (Thorell, 1875) at BugGuide.Net , accessed on April 9, 2020.
- ↑ a b c d Susan C. Jones: Black Widow Spider Ohio State University Extension Fact Sheet (English)
- ↑ a b Gordon M. Nishida and Joann M. Tenorio: What Bit Me? Identifying Hawai'i's Stinging and Biting Insects and Their Kin. University of Hawai'i Press, 1993, pp. 9-12, ISBN 0-82481-492-4
- ↑ a b c B. J. Kaston: Comparative biology of American black widow spiders. Transactions of the San Diego Society of Natural History, 16, 3, pp. 33-82, 1970
- ↑ Heiko Bellmann: Cosmos Atlas Arachnids of Europe. 3rd edition, Franckh-Kosmos, Stuttgart 2006 pp. 76-77 ISBN 3-440-10746-9
- ↑ Latrodectus mactans (Fabricius, 1775) at BugGuide.Net , accessed on April 9, 2020.
- ↑ Toxicological assessment of black widow bites in the Toxinfo database
- ↑ Rainer F. Foelix: Biology of the spiders. Georg Thieme Verlag, Stuttgart 1979 ISBN 3-13-575801-X
- ^ Johan Christian Fabricius: Systema entomologiae, sistens insectorum classes, ordines, genera, species, adiectis, synonymis, locis descriptionibus observationibus . Flensburg et Lipsiae 1775. (Araneae, pp. 431–441)
- ^ Norman I. Platnick: The World Spider Catalog, version 9.0. American Museum of Natural History. Family Theridiidae
- ↑ Black Widow Spiders ( Memento from July 21, 2010 in the Internet Archive )