Western black widow
| Western black widow | ||||||||||||
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Western black widow, female |
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| Latrodectus hesperus | ||||||||||||
| Chamberlin & Ivie , 1935 |
The western black widow ( Latrodectus hesperus ) is a web spider of the crested web spider family (Theridiidae) and was described by Ralph Vary Chamberlin and Wilton Ivie in 1935 . It is common in western North America .
The western black widow is one of the three species into which the North American "black widow" Latrodectus mactans was divided in 1970 after a revision by BJ Kaston. Latrodectus mactans in the narrower sense has since been called the southern black widow , its range borders in the north on that of the northern black widow and in the west on that of the western black widow. The three species differ not only in their area of distribution, but also in specific differences in the pattern.
description
The females reach a body length of 14 to 16 millimeters and have a drawing in the form of a red hourglass on the underside of the abdomen, they are one of the larger widow species. Usually the spider is mainly black in color and otherwise only has a red spot on its back. As the female gets older, the color changes from glossy black to dark brown. The males reach a body length of 8 millimeters and are predominantly light brown to beige. On the abdomen of the male there are three diagonal, pale stripes, here too the color changes. When the male gets older, it resembles the young, which are olive green on the underside.
Occurrence
The distribution area of the western black widow extends from the extreme southwest of Canada through the western regions of the USA to Mexico . It can be found in the east to west of Texas. It is common in the warmer areas of California , Arizona, and other western states.
Western black widows live under ledges, rocks and rubble. They colonize abandoned structures of various rodents or build their nests in quiet areas that are not entered by humans. In some cases, however, they penetrate into populated areas. Sometimes finds of the Western Black Widow are also reported from the suburbs of major American cities.
Way of life
The western black widows usually build their nets near the ground. The animals mainly feed on insects, including large grasshoppers and beetles, but also eat other spiders.
If the adult males are looking for a female, they will not eat anything and will not bite. When they come into contact with a female's web, they show specific communication behavior by generating vibrations with their abdomen. They do not show this behavior when they meet another male's net. The vibrations can be perceived by the female with her cleft sense organs . It is believed that pheromones released with the spider silk indicate to the male whether it is a web from a female of the same species. These pheromones can be absorbed by receptors on the sensory hair on the tarsi and pedipalps .
After mating, the male may be eaten by the larger female. This behavior has led to the name "black widow". However, it happens much less frequently than was previously thought. Then the female lays several hundred eggs, which are covered with cocoons . These cocoons of the western black widow are more egg to pear-shaped and not spherical like those of the southern black widow. They are cream to brownish in color, while in the Southern Black Widow they are gray from the start.
Bite accidents and toxicity
The species is not aggressive but has strong venom. The bite usually feels like a pinprick and is often not noticed at first. Local swellings and muscle cramps are caused, which often only appear after 3 hours. These can last for 48 hours. Deaths are rare. Other symptoms include nausea and sweating.
gallery
male
Close up of a young female
Female with a captured angle spider , on the left a male.
Females, building a net
Individual evidence
- ^ BJ Kaston: Comparative biology of American black widow spiders. Transactions of the San Diego Society of Natural History, 16, 3, pp. 33-82, 1970
- ↑ a b Black Widow Spiders ( Memento from July 21, 2010 in the Internet Archive ) Distinguishing features of the three species (English)
- ↑ Western black widow Pictures of early life stages and adult females and males in the pages of the University of California, Irvine (English)
- ^ The Widow Spiders Darwin K. Vest, Eagle Rock Research, 1999
- ↑ Kenneth Ross and Robert L. Smith: Aspects of the Courtship Behavior of the Black Widow Spider, Latrodectus hesperus (Araneae: Theridiidae), with Evidence for the Existence of a Contact Sex Pheromone. Journal of Arachnology, 7, 1, pp. 69-77, 1979
- ↑ Toxicological assessment of black widow bites in the Toxinfo database
literature
- Ralph Vary Chamberlin and Wilton Ivie: The black widow spider and its varieties in the United States. Bulletin of the University of Utah, 25, 8, Biological series, 3, 1, pp. 1–29, 1935 (first description)
- Norman I. Platnick: The World Spider Catalog, version 9.0. American Museum of Natural History. Family Theridiidae
Web links
Western black widow in the World Spider Catalog
- Latrodectus hesperus - Western Black Widow pictures and description at bugguide.net
- Latrodectus hesperus picture gallery at Tree of Life Web Project (English)
- Western black widow Pictures of juvenile and adult animals on the website of the University of California, Irvine (English)