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Latrodectus is a wide genus of spiders. Johan Christian Fabricius was the first person to describe Latrodectus systemically. Also known as true widows, this group contains the black widow spider, brown widow spider, and similar species. The size of females is significantly larger than males. They are toxic and secrete a fair amount of neurotoxin. Latrodectus is found in almost every corner in the world. They can be found on the ground, below it, or in buildings. Nests of Latrodectus (Spider webs) are usually found on shrubs or trees. The Black Widow is the most poisonous among the Latrodectus genus.

Latrodectus group is broadly characterized by having venom glands in females. These glands are a source of a potent neurotoxin known as latrotoxin. Generally, the bites of the female are harmful and can cause latrodectism in vertebrates. In some cases, this may even lead to the death of a person.

Taxonomy and nomenclature


The Latrodectus genus was first described by Charles Athanase Walkenaer in 1805. Latrodectus belongs to the Theridiidae family, within the Araneae order. Latrodectus is a vast genus which comprises of 32 different types of species such as:

  1. Black widows (Latrodectus mectans)
  2. Red windows (Latrodectus bishopi)
  3. Brown widows (Latrodectus geometricus)
  4. Redback Black Widow (Latrodectus tredecimguttatus)
  5. Western black widow (Latridectus hesperus)

Physical appearance

The size of the body lies in the range of 3 to 10mm, while some females can attain a length of 13mm. The females are different from males in their dark brown color. They change their color from brown to red or orange on the ventral surface of the abdomen. The male is recognized by red and white markings on the underside of the abdomen. The bright marking is absent from the female body. The newly hatched spiderlings are white and their color gradually changes to black. The males of this genus are harmless because they don't possess neurotoxin. Usually, the legs of men are larger than females and the abdomen contains four pairs of white and red stripes.

Distribution, Availability and habitat

Latrodectus is widely spread among different parts of the world except for the Antarctic continent. The adaptive ability of Latrodectus is very high, and they can tolerate extreme temperatures up to more than 70°C. The hot temperature with rainfall and humidity in the environment are ideal conditions for the development of Latrodectus. Latrodectus is assumed to have originated in America. Today, you can find them pretty much anywhere around the world.

That being said, Latrodectus hespersus is commonly found in many parts of the United States. Some species of this genus are found in Canada and Columbia. Generally, there is a wide population of Latrodectus hasselti in the eastern parts of Australia and Asia. The old buildings are the main source of shelter for Latrodectus. The brown widow is native to Southern Africa. The color, body shape, and body-color of Lactrodectus vary from area to area.

Life cycle

The summer or spring season is the best mating time for the Latrodectus. There is a myth among people that females always eat males after mating: this is not correct. Some males can escape from the attack of females. The female uses her web for laying the eggs, for protection from different enemies and harsh environmental conditions.

  • About 400 eggs in a sac are laid by a female.
  • The shape of egg sacs is pear and tan to white color.
  • Generally, nine egg sacs are released by a female in the summer season.
  • The second instar takes 3 to 4 weeks.
  • The process of cannibalism is shown in many species of this genus after 14 days of egg sac formation.
  • The incubation period for eggs is 20 to 30 days.
  • The life span for a female is 180 days and 90 days for males in the Latrodectus genus.
  • A spider can mature in two to four months depending on environmental and other factors, such as the availability of prey.

The females of Latrodectus mactans are different from other species of this genus because of the ability of a black widow spider to store sperm for fertilizing all eggs during her life span. Insects are the main source of their diets. The abdomen size of the male is smaller than females. The females take more molts than males to mature under favorable conditions.


Many birds and lizards are natural enemies of the Latrodectus genus. The egg sacs of black widow spiders are destroyed by a wasp (Baeus latrodecti), and chloropidae fly. The adult spiders are consumed by many wasps such as Chalybio californicum and Tastiotenia festiva. These predators are very important for maintaining the population of Latrodectus under the threshold level. If the population of spiders is not controlled by natural enemies, then the chemical method should be used by spraying some pesticides at the optimum dose as per recommendation according to the label.


Latrodectus feeds on a large number of insects. The woodlice and chilopods are the main diet components of spiders when they attain maturity, and sometimes they feed on arachnids. The web plays an important role in catching the prey because it’s a strong net for holding the prey. When prey is caught in the web, venom is then injected by a spider that leads to paralysis and ultimately death.


Guanosine, Adenosine, Inosine, and Latrotoxins are active components of the venom. From 1850 to 1950 many people died in the world due to toxin secretion by European widow spiders. The mortality rate is about 50% if there is no special care given to the infected person. Chelicerae are a part of the mouthpart in Latrodectus which helps the injection of venom into the body of a living thing. The neurotoxin which is secreted by Latrodectus binds to receptors and causes damage to the nervous system, which leads to many neurological disorders.

Note: You must be careful at the time of handing the webs of Latrodectus. You should wear proper gloves. Consult with an expert doctor if you are bitten by any poisonous spider.

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