Latrodectus hesperus
Western black widow, female
The Western Black Widow ( Latrodectus hesperus ) is a web spider of the family of cobweb spiders ( Theridiidae ) and was described in 1935 by Ralph Vary Chamberlin and Ivie Wilton. It is widespread in western North America.
The Western Black Widow is one of those three ways in which the North American " Black Widow " Latrodectus mactans was split in 1970 following a review by BJ Kaston. Latrodectus mactans in the narrow sense Southern Black Widow has since been called, their range is bordered on the north by the Northern Black Widow and the west by the the Western black widow. The three types differ not only in their area of distribution, but also by differences in the drawing.
Description
The females reach a body length of 14 to 16mm, and have on the underside of the abdomen in the form of a drawing of a red hourglass, it belongs to the larger widow species. Usually the spider is mainly black in color and has otherwise only on the back of a red spot. If the female is older, the color of a shiny black changes to a dark brown. The males reach a body length of 8 millimeters and are mostly light brown to beige. On the abdomen of the male are three diagonal, faded stripes, here too, the coloring changes. If the male is older, so it looks like the pups, which are olive-green on the underside.
Occurrence
The distribution area of the Western Black Widow extends from extreme south-west of Canada on the western regions of the United States to Mexico. In the east it is found to the west of Texas. It is common in the warmer regions of California, Arizona and other Western states.
Western Black Widow live under rock ledges, rocks and boulders. They colonize abandoned buildings of different rodents or build their nests in quiet areas, which are not entered by humans. However the case, they penetrate into populated areas. Sometimes finds the Western black widow also from the suburbs of larger American cities are reported.
Way of life
Your networks to build the Western black widows usually near the ground. The animals feed mainly on insects, including grasshoppers and large beetles, but also eat other spiders.
Are the adult males looking for a female, they take nothing and do not bite. Upon contact with the power of a female they show a specific communication behavior by generating vibrations with their abdomen. This behavior they do not show when they meet on the network of another male. The vibration can be perceived by females with the slit sense organs. It is believed that pheromones, which are delivered by the spin silk, show the male, whether it is a network of a female of the same species. These pheromones can be recorded with receptors of the sensory hairs on the tarsi and the pedipalps.
After mating, it may happen that the male is eaten by the larger females. This behavior has led to the name " Black Widow ". There is, however, instead of much less frequently, is assumed to be earlier. After the female lays several hundred eggs, which are covered with cocoons. These cocoons of the Western black widow are more oval to pear-shaped and not perfectly round as in the Southern Black Widow. They are cream-colored to brownish, while they have in the Southern Black Widow from the beginning a gray tint.
Bite accidents and toxicity
The species is not aggressive, but has a strong poison. The bite feels so mostly like a pinprick and is often not noticed at first. It caused localized swelling and muscle spasms, which often occur after 3 hours. This can last for 48 hours, but deaths are rare. Other symptoms include nausea and sweating.
Gallery
Closeup of a young female
Females captured angle spider, left a male.
Females, the network construction