Latrodectus hesperus

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Latrodectus hesperus
Latrodectus hesperus 1.jpg
Latrodectus hesperus female
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Arachnida
Order: Araneae
Family: Theridiidae
Genus: Latrodectus
Species: L. hesperus
Binomial name
Latrodectus hesperus
Chamberlin & Ivie, 1935[2]

Latrodectus hesperus, the western black widow spider or western widow, is a venomous spider species found in western regions of North America. The female's body is 14–16 mm (1/2 in) in length and is black, often with an hourglass-shaped red mark on the lower abdomen. This "hourglass" mark can be yellow, and on rare occasions, white. The male of the species is around half this length and generally a tan color with lighter striping on the abdomen. The population was previously described as a subspecies of Latrodectus mactans and it is closely related to the northern species Latrodectus variolus. The species, as with others of the genus, build irregular or "messy" webs: Unlike the spiral webs or the tunnel-shaped webs of other spiders, the strands of a Latrodectus web have no apparent organization. Female black widows have potent venom composed of neurotoxins. Fatalities usually only happen with children and the elderly, however medical treatment may be required for others as well. However, the male black widow is harmless to humans. The female's consumption of the male after courtship, a cannibalistic and suicidal behaviour observed in Latrodectus hasseltii (Australia's redback),[3] is rare in this species. Male western widows may breed several times during their relatively short lifespans.[4] Males are known to show preference for mating with well-fed females over starved ones, taking cues from the females' webs.[5]

Taxonomy/Etymology Latrodectus Hesperus also known as black widow or western black widow.


       Kingdom: Animalia

Phylum: arthropoda

Class; arachnida

Order; araneae

Family; theridiidae

Subfamily; lactrodectinae

Genus; latrodectus

Range: You can find the latrodectus Hesperus in western regions of North America.

Sexual behavior: Female stimulates by contact with male webs Male and female Hesperus produce sexually specific scents which are combined with their silk; each sex responds by initiating mating when it comes in contact with a web of the opposite sex.[6]

Feeding: Lactrodectus Hesperus frequently hangs upside down near center of the web and waits for any insects to enter the web to attack. Lactrodectus Hesperus rushes to bite, and wraps the insect in the silk.


Lactrodectus Hesperus has few parasites known to affect them; one is the wasp. The silk for the spider web is beneficial because the insects enter and they can easily attack their prey or parasites.

Interactions with humans: They may often live in human dwellings, usually in cluttered dark areas. Lactrodectus Hesperus has poor eyesight, and they distinguish danger in their habitat by their silk vibration. Only Female Lactrodectus Hesperus have large enough venom glands for a bite to be harmful and require medical treatment.

The ultimate strength and other physical properties of L. hesperus silk were found to be similar to the properties of silk from orb-weaving spiders that had been tested in other studies. The ultimate strength for the three kinds of silk measured in the study was about 1000 MPa. The ultimate strength reported in a previous study for Nephila edulis was 1290 MPa ± 160 MPa[7]



Male western black widow: This image shows the enlarged palpal organs (large dark disks) at the tip of the pedipalps and the spider's eight eyes when the image is expanded.
  1. ^ "Araneoid Egg Case Silk:  A Fibroin with Novel Ensemble Repeat Units from the Black Widow Spider, Latrodectus Hesperus†." - Biochemistry (ACS Publications). Web. 1 Dec. 2014. <>. Johnson, J. C., Patricia J. Trubl, and Lindsay S. Miles. "Black Widows in an Urban Desert: City-Living Compromises Spider Fecundity and Egg Investment Despite Urban Prey Abundance." The American Midland Naturalist 168.2 (2012): 333-40. 2. Kasumovic, Michael M., and Maydianne C. B. Andrade. "Discrimination of Airborne Pheromones by Mate-Searching Male Western Black Widow Spiders (Latrodectus Hesperus ): Species- and Population-Specific Responses." Canadian journal of zoology 82.7 (2004): 1027-34. Rising, Anna, et al. "Spider Silk Proteins: Recent Advances in Recombinant Production, Structure-Function Relationships and Biomedical Applications." Cellular and Molecular Life Sciences 68.2 (2011): 169-84. Ross, Kenneth, and Robert Smith. JSTOR . Saibil, Helen R. "The Black Widow's Versatile Venom." Nature structural biology 7.1 (2000): 3-4. "Species Latrodectus Hesperus - Western Black Widow."
  2. ^ Chamberlin, R. V. & W. Ivie. 1935. The black widow spider and its varieties in the United States. Bull. Univ. Utah 25(8): 1-29. [15, f. 1, 4, 6-14, 21, 23-33]
  3. ^ Andrade, Maydianne C. B. (5 January 1996). "Sexual Selection for Male Sacrifice in the Australian Redback Spider". Science 271 (5245): 70–2. Bibcode:1996Sci...271...70A. doi:10.1126/science.271.5245.70. Retrieved 2007-01-15. 
  4. ^ "Black Widow Spiders". Hastings Reserve. 
  5. ^ Johnson, J. Chadwick; Trubl, Patricia Trubl; Blackmore, Valerie;Miles, Lindsay (2011). "Male black widows court well-fed females more than starved females: silken cues indicate sexual cannibalism risk". Animal Behaviour 82 (2): 383–390. doi:10.1016/j.anbehav.2011.05.018. 
  6. ^ Ross, Kenneth et al. "Aspects of the Courtship Behavior of the Black Widow Spider, Latrodectus hesperus (Araneae: Theridiidae), with Evidence for the Existence of a Contact Sex Pheromone (abstract)". American Arachnological Society. Retrieved 2015-01-22. 
  7. ^ Blackledge, Todd et al. "Quasistatic and continuous dynamic characterization of the mechanical properties of silk from the cobweb of the black widow spider Latrodectus hesperus, table 1". The Company of Biologists. Retrieved 2009-01-23. 
  • Minus, A. 2001. "Latrodectus hesperus" (On-line), Animal Diversity Web. Accessed March 8, 2009
  • Platnick, N. I. 2008. Theridiidae The World Spider Catalog, version 9.0. American Museum of Natural History.

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